[8.x](backport #41229) De-duplicate pipeline steps in system.auth module

[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
• [ ] I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

Disruptive User Impact

None

## Author's Checklist

How to test this PR locally

Run the system tests

mage buildSystemTestBinary
mage docker:ComposeUp
source $(mage PythonVirtualEnv)/bin/activate
INTEGRATION_TESTS=1 BEAT_STRICT_PERMS=false ES_PASS=testing ES_USER=admin TESTING_FILEBEAT_MODULES=system pytest tests/system/test_modules.py

Related issues

• Spitted from Use journald for system module on Debian 12 #41061
• Closes Reduce ingest pipeline duplication in Filebeat's system module #41226

## Use cases
## Screenshots
## Logs

---

This is an automatic backport of pull request #41229 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of f69b501 has failed:

On branch mergify/bp/8.x/pr-41229
Your branch is up to date with 'origin/8.x'.

You are currently cherry-picking commit f69b50127e.
  (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:   filebeat/module/system/auth/ingest/common.yml
	modified:   filebeat/module/system/auth/ingest/pipeline.yml

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	deleted by us:   filebeat/module/system/auth/ingest/entrypoint.yml
	deleted by us:   filebeat/module/system/auth/ingest/journald.yml
	both modified:   filebeat/module/system/auth/manifest.yml

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

[elasticmachine]

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

[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.x/pr-41229 upstream/mergify/bp/8.x/pr-41229
git merge upstream/8.x
git push upstream mergify/bp/8.x/pr-41229