[8.1] [ci-stats] add Client class for accessing test group stats (#125164)

[kibanamachine]

Backport

This is an automatic backport to 8.1 of:

• [ci-stats] add Client class for accessing test group stats #125164

Questions ?

Please refer to the Backport tool documentation

[kibana-ci]

💚 Build Succeeded

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• Commit: ffab539
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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
@kbn/dev-utils	193	200	+7

Public APIs missing exports

Total count of every type that is part of your API that should be exported but is not. This will cause broken links in the API documentation system. Target amount is 0. Run node scripts/build_api_docs --plugin [yourplugin] --stats exports for more detailed information.

id	before	after	diff
@kbn/dev-utils	0	1	+1

Unknown metric groups

API count

id	before	after	diff
@kbn/dev-utils	275	281	+6

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

cc @spalger