Remove bfetch

[lukasolson]

Summary

Relies on #196962 and #197150.
Resolves #186139.

Removes the bfetch plugin & updates documentation accordingly.

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
• Flaky Test Runner was used on any tests changed
• If a plugin configuration key changed, check if it needs to be allowlisted in the cloud and added to the docker list

Risk Matrix

Risk	Probability	Severity	Mitigation/Notes
Multiple Spaces—unexpected behavior in non-default Kibana Space.	Low	High	Integration tests will verify that all features are still supported in non-default Kibana Space and when user switches between spaces.
Multiple nodes—Elasticsearch polling might have race conditions when multiple Kibana nodes are polling for the same tasks.	High	Low	Tasks are idempotent, so executing them multiple times will not result in logical error, but will degrade performance. To test for this case we add plenty of unit tests around this logic and document manual testing procedure.
Code should gracefully handle cases when feature X or plugin Y are disabled.	Medium	High	Unit tests will verify that any feature flag or plugin combination still results in our service operational.
See more potential risk examples

For maintainers

• This was checked for breaking API changes and was labeled appropriately
• This will appear in the Release Notes and follow the guidelines

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💔 Build Failed

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• Commit: 8bd4999

Failed CI Steps

• Build and Validate Next Docs

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/management-settings-ids	136	134	-2

Page load bundle

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

id	before	after	diff
kbnUiSharedDeps-srcJs	3.5MB	3.5MB	-390.0B

Unknown metric groups

API count

id	before	after	diff
@kbn/management-settings-ids	137	135	-2

ESLint disabled line counts

id	before	after	diff
@kbn/test-suites-src	59	57	-2

Total ESLint disabled count

id	before	after	diff
@kbn/test-suites-src	65	63	-2

History

• 💔 Build #259525 failed deacd8d
• 💔 Build #259473 failed deacd8d
• 💔 Build #258981 failed 28d35d4
• 💔 Build #256679 failed ebfc60b
• 💔 Build #256657 failed fd4e9d7

cc @lukasolson

[lukasolson]

Closing in favor of #204285