[serverless] Create Observability Serverless plugin

[clintandrewhall]

Derived from #153274
Builds upon #155582

Summary

This PR creates the Serverless Observability plugin, based on the work from #153274:

• creates the plugin,
• adds API to hide the solution navigation from Enterprise Search,
• calls that API if the chrome style is project.

[elasticmachine]

Pinging @elastic/unified-observability (Team:Observability)

[elasticmachine]

Pinging @elastic/appex-sharedux (Team:SharedUX)

[github-actions]

Documentation preview:

• ✨ Changed pages

[CoenWarmer]

Looks good, but the changes to the page template should only be applied on Observability Shared.

[kibana-ci]

💚 Build Succeeded

• Buildkite Build
• Commit: 3747129

Metrics [docs]

Module Count

Fewer modules leads to a faster build time

id	before	after	diff
serverlessObservability	-	4	+4

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
observabilityShared	142	143	+1
serverlessObservability	-	6	+6
total			+7

Page load bundle

Size of the bundles that are downloaded on every page load. Target size is below 100kb

id	before	after	diff
observabilityShared	21.0KB	21.3KB	+314.0B
serverlessObservability	-	1.5KB	+1.5KB
total			+1.9KB

Unknown metric groups

API count

id	before	after	diff
observabilityShared	142	143	+1
serverlessObservability	-	6	+6
total			+7

ESLint disabled line counts

id	before	after	diff
enterpriseSearch	19	21	+2
securitySolution	399	402	+3
serverlessObservability	-	4	+4
total			+9

Total ESLint disabled count

id	before	after	diff
enterpriseSearch	20	22	+2
securitySolution	479	482	+3
serverlessObservability	-	4	+4
total			+9

History

• 💔 Build #124381 failed c4c86dd
• 💔 Build #124365 failed cf0f9a5
• 💔 Build #124349 failed 839ef70
• 💔 Build #124308 failed 9dd06fc
• 💚 Build #124164 succeeded c4a636d

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

[CoenWarmer]

LGTM!