[9.2](backport #48334) [metricbeat][system] add swap field to system.process.memory metricset

[mergify]

Proposed commit message

See title

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. Where relevant, I have used the stresstest.sh script to run them under stress conditions and race detector to verify their stability.
• I have added an entry in ./changelog/fragments using the changelog tool.

Disruptive User Impact

Author's Checklist

• [ ]

How to test this PR locally

Related issues

Use cases

Screenshots

On Linux

Some validation of the output

As is visible on the screenshot process with PID 43 and 90 really used no swap memory. And process with PID 640 used 1272 kB of swap memory (which is 1302528 bytes) and it matches what is shown in Kibana.

To make sure nothing breaks on other platforms I've run a test on macos (it is working fine, swap field is null on other than Linux platforms)

Logs

---

This is an automatic backport of pull request #48334 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 90844ec has failed:

On branch mergify/bp/9.2/pr-48334
Your branch is up to date with 'origin/9.2'.

You are currently cherry-picking commit 90844ec02.
  (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:
	new file:   changelog/fragments/1767864511-add-swap-field-to-system.process.memory-metric-set-in-metricbeats.yaml
	modified:   docs/reference/metricbeat/exported-fields-system.md
	modified:   docs/reference/metricbeat/metricbeat-metricset-system-process.md
	modified:   metricbeat/module/system/process/_meta/data.json
	modified:   metricbeat/module/system/process/_meta/fields.yml

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

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

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🔍 Preview links for changed docs

• docs/reference/metricbeat/exported-fields-system.md
• docs/reference/metricbeat/metricbeat-metricset-system-process.md