Create Multi-Device Explore from Glean activity data

[ksiegler1]

Checklist for reviewer:

When adding a new derived dataset:

• Ensure that the data is not available already (fully or partially) and recommend extending an existing dataset in favor of creating new ones. Data may be available in bigquery-etl repository, looker-hub or in looker-spoke-default.
• Avoid merging a PR that includes the logic of a core metric or complex business logic. The recommendation is to implement core business logic in bigquery-etl. E.g. The type of search or the calculation of DAU or visited URIs.
• Avoid merging code in Looker Explores/Views that implement analysis with multiple lines of code or that will be likely replicated in the future. Instead, aim for extending an existing dataset to include the required logic, and use Looker aggregates to facilitate the analysis.
• Avoid merging a PR with logic that requires validation and health checks. It is recommended to implement it in bigquery-etl for full test coverage and failure alerts.

[akkomar]

This uses mozdata.accounts_backend.accounts_events in a temporary derived table which will eventually result in low performance, same like with some of the current dashboards based on the legacy telemetry.
Can we instead add devices to users_services_daily and use this table here?

[ksiegler1]

Based on our previous discussions, we agreed to keep this as is for now and update when the new derived tables become available to improve performance.

[akkomar]

I'm going to push back on this as it seems to be fairly easy to add to users_services_daily now when we have this table.
I took a stab at this in mozilla/bigquery-etl#5131 - can you take a look?