[metricbeat][system/process, system/process_summary]: mark module as healthy if metrics are partially filled

[VihasMakwana]

• Bug

Proposed commit message

• If metrics are partially available for system.process and system.process_summary, do not mark metricset as degraded.
• Instead, keep it healthy and display the message

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.

How to test this PR locally

• Clone from this branch
• Do mage package from x-pack/agentbeat
• Run elastic agent with new agentbeat binary
• Run as unprivileged mode, and run elastic-agent status --output=json
• You should see HEALTHY state and error message displayed

Related issues

• Closes [Elastic Agent] The system process metricsets should not report as degraded when metrics are partially collected #40542

Use cases

Screenshots

[mergify]

This pull request does not have a backport label.
If this is a bug or security fix, could you label this PR @VihasMakwana? 🙏.
For such, you'll need to label your PR with:

• The upcoming major version of the Elastic Stack
• The upcoming minor version of the Elastic Stack (if you're not pushing a breaking change)

To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-v8./d.0 is the label to automatically backport to the 8./d branch. /d is the digit

[elasticmachine]

Pinging @elastic/elastic-agent-data-plane (Team:Elastic-Agent-Data-Plane)

[leehinman]

Needs a changelog entry

[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 show-healthy-if-partial upstream/show-healthy-if-partial
git merge upstream/main
git push upstream show-healthy-if-partial