[8.x] [Feature Flags Service] Hello world 👋 (#188562)

[afharo]

Backport

This will backport the following commits from main to 8.x:

• [Feature Flags Service] Hello world 👋 (#188562)

Questions ?

Please refer to the Backport tool documentation

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Metrics [docs]

Module Count

Fewer modules leads to a faster build time

id	before	after	diff
cloudExperiments	10	13	+3
core	442	447	+5
total			+8

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
@kbn/core-http-request-handler-context-server	13	0	-13

Async chunks

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

id	before	after	diff
cloudExperiments	52.6KB	0.0B	-52.6KB
core	65.3KB	60.9KB	-4.4KB
total			-56.9KB

Page load bundle

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

id	before	after	diff
cloudExperiments	7.8KB	92.4KB	+84.6KB
core	418.2KB	454.5KB	+36.3KB
total			+121.0KB

Unknown metric groups

API count

id	before	after	diff
@kbn/core-feature-flags-browser	-	29	+29
@kbn/core-feature-flags-browser-internal	-	9	+9
@kbn/core-feature-flags-browser-mocks	-	4	+4
@kbn/core-feature-flags-server	-	38	+38
@kbn/core-feature-flags-server-internal	-	11	+11
@kbn/core-feature-flags-server-mocks	-	6	+6
@kbn/core-http-request-handler-context-server	16	17	+1
@kbn/core-lifecycle-browser	36	38	+2
@kbn/core-lifecycle-server	40	42	+2
cloudExperiments	12	0	-12
total			+90

async chunk count

id	before	after	diff
cloudExperiments	1	0	-1
core	2	1	-1
total			-2

ESLint disabled line counts

id	before	after	diff
cloudExperiments	3	2	-1

References to deprecated APIs

id	before	after	diff
cloudChat	4	0	-4
observabilityOnboarding	3	1	-2
securitySolution	472	470	-2
total			-8

Total ESLint disabled count

id	before	after	diff
cloudExperiments	3	2	-1

Unreferenced deprecated APIs

id	before	after	diff
cloudExperiments	1	0	-1

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@elasticmachine merge upstream