[7.x](backport #28368) [Metricbeat] gcp.gke: uniform metric's fields

[mergify]

This is an automatic backport of pull request #28368 done by Mergify.
Cherry-pick of 568fd05 has failed:

On branch mergify/bp/7.x/pr-28368
Your branch is up to date with 'origin/7.x'.

You are currently cherry-picking commit 568fd05e68.
  (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:   x-pack/metricbeat/module/gcp/_meta/fields.yml
	modified:   x-pack/metricbeat/module/gcp/gke/_meta/fields.yml
	new file:   x-pack/metricbeat/module/gcp/gke/gke_integration_test.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   metricbeat/docs/fields.asciidoc
	both modified:   x-pack/metricbeat/module/gcp/fields.go

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

---

Mergify commands and options

More conditions and actions can be found in the documentation.

You can also trigger Mergify actions by commenting on this pull request:

• @Mergifyio refresh will re-evaluate the rules
• @Mergifyio rebase will rebase this PR on its base branch
• @Mergifyio update will merge the base branch into this PR
• @Mergifyio backport <destination> will backport this PR on <destination> branch

Additionally, on Mergify dashboard you can:

• look at your merge queues
• generate the Mergify configuration with the config editor.

Finally, you can contact us on https://mergify.io/

[elasticmachine]

💚 Build Succeeded

the below badges are clickable and redirect to their specific view in the CI or DOCS

Expand to view the summary

Build stats

• Duration: 46 min 49 sec

❕ Flaky test report

No test was executed to be analysed.

🤖 GitHub comments

To re-run your PR in the CI, just comment with:

• /test : Re-trigger the build.

• /package : Generate the packages and run the E2E tests.

• /beats-tester : Run the installation tests with beats-tester.

[endorama]

/test

[elasticmachine]

Pinging @elastic/integrations (Team:Integrations)