[8.16](backport #4384) Add docs for new central log source setting

[mergify]

Description

Document the new Kibana log source advanced setting that provides a centralized place to store log index patterns that other solutions can access instead of hardcoding index patterns in different places.

This PR updates all of the places in the o11y docs where we were documenting using hardcoded log index patterns and replaces them with the logs source setting.

We will need to update the Kibana advanced settings in another PR. The Discover docs may need an update as well.

Documentation sets edited in this PR

Check all that apply.

• Stateful (docs/en/observability/*)
• Serverless (docs/en/serverless/*)
• Integrations Developer Guide (docs/en/integrations/*)
• None of the above

Related issue

Closes #4316

Follow-up tasks

Select one.

• This PR does not need to be ported to another doc set because:
  • The concepts in this PR only apply to one doc set (serverless or stateful)
  • The PR contains edits to both doc sets (serverless and stateful)
• This PR needs to be ported to another doc set:
  • Port to stateful docs: <link to PR or tracking issue>
  • Port to serverless docs: <link to PR or tracking issue>

---

This is an automatic backport of pull request #4384 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 0fb7cdd has failed:

On branch mergify/bp/8.16/pr-4384
Your branch is up to date with 'origin/8.16'.

You are currently cherry-picking commit 0fb7cdd0.
  (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:   docs/en/observability/categorize-logs.asciidoc
	modified:   docs/en/observability/configure-logs-sources.asciidoc
	modified:   docs/en/observability/explore-logs.asciidoc
	modified:   docs/en/observability/inspect-log-anomalies.asciidoc

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	deleted by us:   docs/en/serverless/logging/view-and-monitor-logs.mdx

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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