[8.x](backport #5443) mage: check that links are live in the OTel README

[mergify]

This PR adds a utility based on the link-patrol command to check if links in a given file are live. This utility should be reusable so we can use it to validate other files in the repository.

Also added a check in the check and otel:readme mage targets to validate all links in the Otel Readme are valid.

What does this PR do?

Why is it important?

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in ./changelog/fragments using the changelog tool
• I have added an integration test or an E2E test

How to test this PR locally

You can either run mage check or mage otel:readme to trigger the link check.

To test it indeed fails if a link is invalid you can introduce a typo and it should fail in subsequent runs.

sed -i 's/featuregate/fff/' internal/pkg/otel/templates/README.md.tmpl

Related issues

• Closes Automatically verify links in OTel README file #5117

  ---

  This is an automatic backport of pull request mage: check that links are live in the OTel README #5443 done by Mergify.

[mergify]

Cherry-pick of 835cd9c has failed:

On branch mergify/bp/8.x/pr-5443
Your branch is up to date with 'origin/8.x'.

You are currently cherry-picking commit 835cd9c0bf.
  (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:   NOTICE.txt
	modified:   dev-tools/mage/check.go
	new file:   dev-tools/mage/gotool/linkcheck.go
	modified:   dev-tools/mage/install.go
	modified:   magefile.go
	modified:   tools/tools.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   go.mod
	both modified:   go.sum

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

[mauri870]

There are conflicts in this branch, leaving on hold until I fix them.

[mergify]

This pull request is now in conflicts. Could you fix it? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

git fetch upstream
git checkout -b mergify/bp/8.x/pr-5443 upstream/mergify/bp/8.x/pr-5443
git merge upstream/8.x
git push upstream mergify/bp/8.x/pr-5443

[mauri870]

/test

[mergify]

This pull request is now in conflicts. Could you fix it? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

git fetch upstream
git checkout -b mergify/bp/8.x/pr-5443 upstream/mergify/bp/8.x/pr-5443
git merge upstream/8.x
git push upstream mergify/bp/8.x/pr-5443

[mergify]

This pull request has not been merged yet. Could you please review and merge it @mauri870? 🙏

[elastic-sonarqube]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarQube