[8.19] (backport #11328) Add notes on configuration compatibility

[mergify]

What does this PR do?

Adds notes on Collector config compatibility for Elastic Stack versions.

Why is it important?

Incompatible Collector 9.x configs can be breaking changes for ELK 8.x users.

Related: elastic/opentelemetry#495

---

This is an automatic backport of pull request #11328 done by Mergify.

[mergify]

Cherry-pick of 319e0f5 has failed:

On branch mergify/bp/8.19/pr-11328
Your branch is up to date with 'origin/8.19'.

You are currently cherry-picking commit 319e0f566.
  (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)

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	deleted by us:   docs/reference/edot-collector/components.md
	deleted by us:   docs/reference/edot-collector/config/default-config-k8s.md
	both modified:   docs/reference/edot-collector/config/default-config-standalone.md

no changes added to commit (use "git add" and/or "git commit -a")

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

[mergify]

This pull request has not been merged yet. Could you please review and merge it @theletterf? 🙏