Cherry-pick #19114 to 7.x: Rename to management.Manager, add UpdateStatus to Manager interface.

[blakerouse]

Cherry-pick of PR #19114 to 7.x branch. Original message:

What does this PR do?

Renames management.ConfigManager to management.Manager being that it now does more than just manage configurations. Adds UpdateStatus to management.Manager to allow a beat to update the status.

Using FleetManager the status will be propagated over the elastic-agent-client to the controlling agent.

Why is it important?

So status can be reported both to the controlling Agent and up to Fleet for observability of the beats that Agent is running.

Reporting a Failed status to Agent will result in the Agent stopping and restarting the beat.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

Author's Checklist

• [ ]

How to test this PR locally

Related issues

• Closes [Agent] Implement an HealthCheck function in every beats. #17737

Use cases

Screenshots

Logs

[elasticmachine]

Pinging @elastic/integrations-services (Team:Services)

[elasticmachine]

Pinging @elastic/ingest-management (Team:Ingest Management)

[elasticmachine]

💚 Build Succeeded

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Build stats

• Build Cause: [Pull request #19172 opened]

• Start Time: 2020-06-12T17:24:24.964+0000

• Duration: 80 min 4 sec

Test stats 🧪

Test	Results
Failed	0
Passed	6691
Skipped	1069
Total	7760

Steps errors

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• Name: Report to Codecov

  • Description: curl -sSLo codecov https://codecov.io/bash for i in auditbeat filebeat heartbeat libbeat metricbeat packetbeat winlogbeat journalbeat do FILE="${i}/build/coverage/full.cov" if [ -f "${FILE}" ]; then bash codecov -f "${FILE}" fi done

  • Duration: 2 min 22 sec

  • Start Time: 2020-06-12T18:41:33.837+0000

  • log

• Name: Report to Codecov

  • Description: curl -sSLo codecov https://codecov.io/bash for i in auditbeat filebeat heartbeat libbeat metricbeat packetbeat winlogbeat journalbeat do FILE="${i}/build/coverage/full.cov" if [ -f "${FILE}" ]; then bash codecov -f "${FILE}" fi done

  • Duration: 2 min 22 sec

  • Start Time: 2020-06-12T18:05:36.408+0000

  • log

[ph]

LGTM, backport looks fine.