[8.15](backport #40400) [metricbeat] - Allow metricsets to report their status via v2 protocol

[mergify]

Proposed commit message

• Add StatusReporter for letting individual metricsets to report their statuses.
• Add NonFatalError support for system/process summary
  • See [system/process] add support for mutlierr  elastic-agent-system-metrics#172 for non-fatal errors.

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.

Disruptive User Impact

Author's Checklist

• [ ]

How to test this PR locally

• How to test with agent:
  • Build agentbeat locally from this branch.
  • Download/Build elastic-agent.
  • Put the agentbeat binary in elastic-agent/data/elastic-agent-*/components/
  • Install the agent in unprivileged mode and observe the health.
    • You should see DEGRADED state in a couple of minutes.
    • You should also see non-fatal error fetching PID metrics and permission denied errors.

Related issues

• Closes [Elastic Agent] Allow Metricbeat metricsets to report their status to the Elastic Agent #39736
• Closes [Elastic Agent] The system/metrics input should report itself as degraded when it encounters a permissions error #39737

Use cases

Screenshots

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This is an automatic backport of pull request #40400 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 2060383 has failed:

On branch mergify/bp/8.15/pr-40400
Your branch is up to date with 'origin/8.15'.

You are currently cherry-picking commit 2060383cc2.
  (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:   metricbeat/helper/http_test.go
	modified:   metricbeat/mb/mb.go
	modified:   metricbeat/mb/module/runner.go
	modified:   metricbeat/mb/module/runner_group.go
	modified:   metricbeat/mb/module/wrapper.go
	modified:   metricbeat/mb/testing/modules.go
	modified:   metricbeat/module/elasticsearch/node_stats/data_test.go
	modified:   metricbeat/module/system/process/process.go
	modified:   metricbeat/module/system/process/process_test.go
	modified:   metricbeat/module/system/process_summary/process_summary.go
	modified:   metricbeat/module/system/process_summary/process_summary_test.go
	modified:   metricbeat/module/system/test_system.py
	new file:   x-pack/libbeat/management/tests/mbtest/system/process_integration_test.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   NOTICE.txt
	both modified:   go.mod
	both modified:   go.sum

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[botelastic]

This pull request doesn't have a Team:<team> label.

[mergify]

This pull request is now in conflicts. Could you fix it? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

git fetch upstream
git checkout -b mergify/bp/8.15/pr-40400 upstream/mergify/bp/8.15/pr-40400
git merge upstream/8.15
git push upstream mergify/bp/8.15/pr-40400

[mergify]

This pull request has not been merged yet. Could you please review and merge it @VihasMakwana? 🙏

[cmacknz]

Closing this, this needs to be in 8.16.0 given the number of issues it is finding for us that we need to address.