[8.18] (backport #16788) ci: use manual caching with actions/cache

[mergify]

Motivation/summary

use os agnostic cache key
only cache pkg mod cache

Checklist

• Update CHANGELOG.asciidoc
• Documentation has been updated

For functional changes, consider:

• Is it observable through the addition of either logging or metrics?
• Is its use being published in telemetry to enable product improvement?
• Have system tests been added to avoid regression?

How to test these changes

Related issues

---

This is an automatic backport of pull request #16788 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of bac9fec has failed:

On branch mergify/bp/8.18/pr-16788
Your branch is up to date with 'origin/8.18'.

You are currently cherry-picking commit bac9fec6.
  (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 <file>..." to mark resolution)
	both modified:   .github/workflows/ci.yml

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 @kruskall? 🙏