[7.x] Add ML usage collector descriptions to the schema. (#100387)

[pjhampton]

Backports the following commits to 7.x:

• Add ML usage collector descriptions to the schema. (Add ML usage collector descriptions to the schema. #100387)

[kibanamachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request
• Commit: 83068bd
• Storybooks Preview

Metrics [docs]

Unknown metric groups

References to deprecated APIs

id	before	after	diff
canvas	29	25	-4
crossClusterReplication	8	6	-2
globalSearch	4	2	-2
indexManagement	12	7	-5
lens	67	45	-22
licensing	18	15	-3
lists	239	236	-3
ml	121	115	-6
monitoring	109	56	-53
securitySolution	386	342	-44
stackAlerts	101	95	-6
total			-150

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@elasticmachine merge upstream