[8.8] [APM] Mark Agent explorer as beta (#156470)

[kibanamachine]

Backport

This will backport the following commits from main to 8.8:

• [APM] Mark Agent explorer as beta (#156470)

Questions ?

Please refer to the Backport tool documentation

[elasticmachine]

Pinging @elastic/apm-ui (Team:APM)

[kibana-ci]

💚 Build Succeeded

• Buildkite Build
• Commit: add3051

Metrics [docs]

Public APIs missing comments

Total count of every public API that lacks a comment. Target amount is 0. Run node scripts/build_api_docs --plugin [yourplugin] --stats comments for more detailed information.

id	before	after	diff
observability	552	551	-1

Async chunks

Total size of all lazy-loaded chunks that will be downloaded as the user navigates the app

id	before	after	diff
apm	3.5MB	3.5MB	-35.0B

Unknown metric groups

API count

id	before	after	diff
observability	558	557	-1

ESLint disabled line counts

id	before	after	diff
enterpriseSearch	17	19	+2
securitySolution	399	402	+3
total			+5

Total ESLint disabled count

id	before	after	diff
enterpriseSearch	18	20	+2
securitySolution	479	482	+3
total			+5

To update your PR or re-run it, just comment with:
@elasticmachine merge upstream

cc @yngrdyn