[8.x] [embeddable] remove legacy embeddable compatibility layer (#204642)

[kibanamachine]

Backport

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

• [embeddable] remove legacy embeddable compatibility layer (#204642)

Questions ?

Please refer to the Backport tool documentation

[elasticmachine]

💛 Build succeeded, but was flaky

• Buildkite Build
• Commit: 48c1d31

Failed CI Steps

• FTR Configs #25

Test Failures

• [job] [logs] FTR Configs #25 / InfraOps App Metrics UI Node Details #Asset Type: host Processes Tab should render processes tab and with Total Value summary

Metrics [docs]

Module Count

Fewer modules leads to a faster build time

id	before	after	diff
embeddable	132	130	-2

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
embeddable	338	291	-47

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
embeddable	5	4	-1

Page load bundle

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

id	before	after	diff
embeddable	55.5KB	49.0KB	-6.5KB

Unknown metric groups

API count

id	before	after	diff
embeddable	424	377	-47

References to deprecated APIs

id	before	after	diff
embeddable	11	9	-2

cc @nreese