Move ItemBuffer to package

[lukasolson]

Summary

Part of #186139.

Bfetch exports ItemBuffer and TimedItemBuffer, the latter of which is also used inside of the content management plugin.

After bfetch is removed, content management will be the sole consumer, which is why I've added the team ownership to be appex-sharedux.

Checklist

• Documentation was added for features that require explanation or tutorials
• Unit or functional tests were updated or added to match the most common scenarios

[elasticmachine]

Pinging @elastic/kibana-data-discovery (Team:DataDiscovery)

[elasticmachine]

💚 Build Succeeded

• Buildkite Build
• Commit: e32967f

Metrics [docs]

Module Count

Fewer modules leads to a faster build time

id	before	after	diff
bfetch	25	27	+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
@kbn/item-buffer	-	14	+14
bfetch	73	59	-14
total			-0

Unknown metric groups

API count

id	before	after	diff
@kbn/item-buffer	-	23	+23
bfetch	83	60	-23
total			-0

History

• 💛 Build #243285 was flaky 4da6ea7
• 💔 Build #243229 failed 545605b
• 💔 Build #242906 failed bac6048

cc @lukasolson

[Dosant]

thanks!