[8.x](backport #4437) Update references to apps and pages

[mergify]

Description

Applies style guidelines from referring to apps and pages to the Observability docs.

Documentation sets edited in this PR

Check all that apply.

• Stateful (docs/en/observability/*)
• Serverless (docs/en/serverless/*)
• Integrations Developer Guide (docs/en/integrations/*)
• None of the above

Related issue

Closes #4358

Checklist

• Product/Engineering Review
• Writer Review

Follow-up tasks

Select one.

• This PR does not need to be ported to another doc set because:
  • The concepts in this PR only apply to one doc set (serverless or stateful)
  • The PR contains edits to both doc sets (serverless and stateful)
• This PR needs to be ported to another doc set:
  • Port to stateful docs: <link to PR or tracking issue>
  • Port to serverless docs: <link to PR or tracking issue>

---

This is an automatic backport of pull request #4437 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 0a1da4a has failed:

On branch mergify/bp/8.x/pr-4437
Your branch is up to date with 'origin/8.x'.

You are currently cherry-picking commit 0a1da4a9.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   docs/en/observability/apm/collect-application-data/open-telemetry/otel-metrics.asciidoc
	modified:   docs/en/observability/apm/configure/shared/input-apm.asciidoc
	modified:   docs/en/observability/apm/manage-storage/custom-index-template.asciidoc
	modified:   docs/en/observability/apm/manage-storage/ilm-how-to.asciidoc
	modified:   docs/en/observability/apm/manage-storage/reduce-apm-storage.asciidoc
	modified:   docs/en/observability/apm/security/apm-agents/api-keys.asciidoc
	modified:   docs/en/observability/apm/security/data-security/apm-spaces.asciidoc
	modified:   docs/en/observability/apm/security/data-security/custom-filter.asciidoc
	modified:   docs/en/observability/apm/security/elastic-stack/access-api-keys.asciidoc
	modified:   docs/en/observability/apm/tab-widgets/jaeger.asciidoc
	modified:   docs/en/observability/apm/upgrading-to-integration.asciidoc
	modified:   docs/en/observability/apm/view-and-analyze/filter-and-search/cross-cluster-search.asciidoc
	modified:   docs/en/observability/apm/view-and-analyze/inventory.asciidoc
	modified:   docs/en/observability/apm/view-and-analyze/ui-overview/services.asciidoc
	modified:   docs/en/observability/categorize-logs.asciidoc
	modified:   docs/en/observability/cloud-monitoring/aws/ingest-aws-firehose.asciidoc
	modified:   docs/en/observability/cloud-monitoring/aws/monitor-amazon-ec2.asciidoc
	modified:   docs/en/observability/cloud-monitoring/aws/monitor-amazon-kinesis.asciidoc
	modified:   docs/en/observability/cloud-monitoring/aws/monitor-amazon-s3.asciidoc
	modified:   docs/en/observability/cloud-monitoring/aws/monitor-aws-agent.asciidoc
	modified:   docs/en/observability/cloud-monitoring/aws/monitor-aws-beats.asciidoc
	modified:   docs/en/observability/cloud-monitoring/aws/monitor-aws-cloudtrail-firehose.asciidoc
	modified:   docs/en/observability/cloud-monitoring/aws/monitor-aws-cloudwatch-firehose.asciidoc
	modified:   docs/en/observability/cloud-monitoring/aws/monitor-aws-esf.asciidoc
	modified:   docs/en/observability/cloud-monitoring/aws/monitor-aws-firewall-firehose.asciidoc
	modified:   docs/en/observability/cloud-monitoring/aws/monitor-aws-waf-firehose.asciidoc
	modified:   docs/en/observability/cloud-monitoring/azure/monitor-azure-agent.asciidoc
	modified:   docs/en/observability/cloud-monitoring/azure/monitor-azure-beats.asciidoc
	modified:   docs/en/observability/cloud-monitoring/azure/monitor-azure-native.asciidoc
	modified:   docs/en/observability/cloud-monitoring/azure/monitor-azure-openai-apm.asciidoc
	modified:   docs/en/observability/cloud-monitoring/azure/monitor-azure-openai.asciidoc
	modified:   docs/en/observability/configure-logs-sources.asciidoc
	modified:   docs/en/observability/create-alerts.asciidoc
	modified:   docs/en/observability/explore-logs.asciidoc
	modified:   docs/en/observability/gcp-dataflow.asciidoc
	modified:   docs/en/observability/handle-no-results-found-message.asciidoc
	deleted:    docs/en/observability/images/EC2-logs.png
	deleted:    docs/en/observability/images/agent-tut-azure-activity-log-columns.png
	deleted:    docs/en/observability/images/agent-tut-azure-activity-logs.png
	deleted:    docs/en/observability/images/kibana-home.png
	deleted:    docs/en/observability/images/monitor-azure-kibana-logs-app.png
	deleted:    docs/en/observability/images/monitor-azure-kibana-observability-page-data.png
	deleted:    docs/en/observability/images/monitor-azure-native-kibana-logs-app.png
	deleted:    docs/en/observability/images/monitor-azure-native-kibana-vms-metrics-detail.png
	deleted:    docs/en/observability/images/monitor-azure-native-kibana-vms-metrics.png
	modified:   docs/en/observability/inspect-log-anomalies.asciidoc
	modified:   docs/en/observability/inventory-threshold-alert.asciidoc
	modified:   docs/en/observability/logs-add-service-name.asciidoc
	modified:   docs/en/observability/logs-app-fields.asciidoc
	modified:   docs/en/observability/logs-ecs-application.asciidoc
	modified:   docs/en/observability/logs-index-template.asciidoc
	modified:   docs/en/observability/logs-metrics-get-started.asciidoc
	modified:   docs/en/observability/logs-monitor-datasets.asciidoc
	modified:   docs/en/observability/logs-parse.asciidoc
	modified:   docs/en/observability/logs-plaintext.asciidoc
	modified:   docs/en/observability/logs-threshold-alert.asciidoc
	modified:   docs/en/observability/manage-cases.asciidoc
	modified:   docs/en/observability/metrics-app-fields.asciidoc
	modified:   docs/en/observability/metrics-threshold-alert.asciidoc
	modified:   docs/en/observability/monitor-infra/analyze-hosts.asciidoc
	modified:   docs/en/observability/monitor-infra/aws-metrics.asciidoc
	modified:   docs/en/observability/monitor-infra/configure-metrics-sources.asciidoc
	modified:   docs/en/observability/monitor-infra/explore-metrics.asciidoc
	modified:   docs/en/observability/monitor-infra/inspect-metric-anomalies.asciidoc
	modified:   docs/en/observability/monitor-infra/monitor-infrastructure-and-hosts.asciidoc
	modified:   docs/en/observability/monitor-infra/view-infrastructure-metrics.asciidoc
	modified:   docs/en/observability/monitor-k8s/monitor-k8s-add-integration.asciidoc
	modified:   docs/en/observability/monitor-k8s/monitor-k8s-application-performance.asciidoc
	modified:   docs/en/observability/monitor-k8s/monitor-k8s-explore-logs-and-metrics.asciidoc
	modified:   docs/en/observability/monitor-logs.asciidoc
	modified:   docs/en/observability/monitor-nginx-ml.asciidoc
	modified:   docs/en/observability/monitor-nginx.asciidoc
	modified:   docs/en/observability/monitor-status-alert.asciidoc
	modified:   docs/en/observability/observability-ai-assistant.asciidoc
	modified:   docs/en/observability/profiling-index-lifecycle-management.asciidoc
	modified:   docs/en/observability/profiling-upgrade.asciidoc
	modified:   docs/en/observability/quickstarts/monitor-hosts-with-elastic-agent.asciidoc
	modified:   docs/en/observability/quickstarts/monitor-k8s-logs-metrics.asciidoc
	modified:   docs/en/observability/slo-create.asciidoc
	modified:   docs/en/observability/slo-privileges.asciidoc
	modified:   docs/en/observability/splunk-get-started.asciidoc
	modified:   docs/en/observability/synthetics-analyze.asciidoc
	modified:   docs/en/observability/synthetics-configuration.asciidoc
	modified:   docs/en/observability/synthetics-get-started-project.asciidoc
	modified:   docs/en/observability/synthetics-get-started-ui.asciidoc
	modified:   docs/en/observability/synthetics-private-location.asciidoc
	modified:   docs/en/observability/synthetics-reference/lightweight-config/common.asciidoc
	modified:   docs/en/observability/tab-widgets/add-apm-integration/content.asciidoc
	modified:   docs/en/observability/tail-logs.asciidoc
	modified:   docs/en/observability/threshold-alert.asciidoc
	modified:   docs/en/observability/triage-slo-burn-rate-breaches.asciidoc
	modified:   docs/en/observability/triage-threshold-breaches.asciidoc
	modified:   docs/en/observability/universal-profiling.asciidoc
	modified:   docs/en/observability/uptime-duration-anomaly-alert.asciidoc
	modified:   docs/en/observability/uptime-tls-alert.asciidoc
	modified:   docs/en/shared/install-configure-filebeat.asciidoc
	modified:   docs/en/shared/install-configure-metricbeat.asciidoc
	modified:   docs/en/shared/integrations-quick-guide.asciidoc

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   docs/en/observability/logs-filter.asciidoc

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

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