[7.x](backport #25696) Remove Beats central management

[mergify]

This is an automatic backport of pull request #25696 done by Mergify.
Cherry-pick of 27e76c5 has failed:

On branch mergify/bp/7.x/pr-25696
Your branch is up to date with 'origin/7.x'.

You are currently cherry-picking commit 27e76c567.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   CHANGELOG.next.asciidoc
	modified:   filebeat/docs/howto/load-ingest-pipelines.asciidoc
	modified:   filebeat/docs/index.asciidoc
	deleted:    libbeat/docs/shared-central-management.asciidoc
	modified:   metricbeat/docs/index.asciidoc
	modified:   x-pack/auditbeat/cmd/root.go
	modified:   x-pack/elastic-agent/pkg/agent/program/supported.go
	modified:   x-pack/elastic-agent/spec/apm-server.yml
	modified:   x-pack/elastic-agent/spec/filebeat.yml
	modified:   x-pack/elastic-agent/spec/heartbeat.yml
	modified:   x-pack/elastic-agent/spec/metricbeat.yml
	modified:   x-pack/elastic-agent/spec/osquerybeat.yml
	modified:   x-pack/elastic-agent/spec/packetbeat.yml
	modified:   x-pack/filebeat/cmd/root.go
	modified:   x-pack/heartbeat/cmd/root.go
	modified:   x-pack/journalbeat/cmd/root.go
	deleted:    x-pack/libbeat/cmd/enroll.go
	deleted:    x-pack/libbeat/cmd/inject.go
	modified:   x-pack/libbeat/libbeat.go
	deleted:    x-pack/libbeat/management/api/auth_client.go
	deleted:    x-pack/libbeat/management/api/auth_client_test.go
	deleted:    x-pack/libbeat/management/api/client.go
	deleted:    x-pack/libbeat/management/api/client_test.go
	deleted:    x-pack/libbeat/management/api/configuration.go
	deleted:    x-pack/libbeat/management/api/configuration_test.go
	deleted:    x-pack/libbeat/management/api/convert.go
	deleted:    x-pack/libbeat/management/api/convert_test.go
	deleted:    x-pack/libbeat/management/api/doc.go
	deleted:    x-pack/libbeat/management/api/enroll.go
	deleted:    x-pack/libbeat/management/api/enrollment_token.go
	deleted:    x-pack/libbeat/management/api/enrollment_token_test.go
	deleted:    x-pack/libbeat/management/api/event_reporter.go
	deleted:    x-pack/libbeat/management/api/event_reporter_test.go
	deleted:    x-pack/libbeat/management/api/response.go
	modified:   x-pack/libbeat/management/blacklist.go
	modified:   x-pack/libbeat/management/blacklist_test.go
	deleted:    x-pack/libbeat/management/cache.go
	deleted:    x-pack/libbeat/management/cache_test.go
	modified:   x-pack/libbeat/management/config.go
	deleted:    x-pack/libbeat/management/config_test.go
	deleted:    x-pack/libbeat/management/enroll.go
	deleted:    x-pack/libbeat/management/error.go
	deleted:    x-pack/libbeat/management/error_test.go
	deleted:    x-pack/libbeat/management/fleet/config.go
	deleted:    x-pack/libbeat/management/fleet/manager.go
	deleted:    x-pack/libbeat/management/fleet/manager_test.go
	deleted:    x-pack/libbeat/management/fleet/plugin.go
	modified:   x-pack/libbeat/management/manager.go
	modified:   x-pack/libbeat/management/manager_test.go
	modified:   x-pack/libbeat/management/plugin.go
	deleted:    x-pack/libbeat/management/state.go
	deleted:    x-pack/libbeat/management/state_test.go
	deleted:    x-pack/libbeat/tests/system/base.py
	deleted:    x-pack/libbeat/tests/system/config/mockbeat.yml.j2
	deleted:    x-pack/libbeat/tests/system/requirements.txt
	deleted:    x-pack/libbeat/tests/system/test_management.py
	modified:   x-pack/metricbeat/cmd/root.go
	modified:   x-pack/osquerybeat/cmd/root.go
	modified:   x-pack/packetbeat/cmd/root.go

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	both modified:   x-pack/libbeat/include/include.go
	deleted by them: x-pack/libbeat/management/api/enroll_test.go
	both modified:   x-pack/winlogbeat/cmd/root.go

To fix up this pull request, you can check it out locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

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[elasticmachine]

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• Build Cause: michel-laterman commented: /test

• Start Time: 2021-06-01T19:29:13.019+0000

• Duration: 66 min 4 sec

• Commit: 6a55ac1

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Test	Results
Failed	0
Passed	15
Skipped	16
Total	31

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Test	Results
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Passed	15
Skipped	16
Total	31

[urso]

Looks like Kibana still needs to clean their docs in the 7.x branch.

[michel-laterman]

/test

[michel-laterman]

/test

[michel-laterman]

@elasticmachine run docs build

[michel-laterman]

@elasticmachine run elasticsearch-ci/docs