[8.19] (backport #16705) test: use logp test logger in tests

[mergify]

Motivation/summary

global logger is deprecated, use testing logger

helps with the new breaking changes coming from beats

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 #16705 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 8f64c3c has failed:

On branch mergify/bp/8.19/pr-16705
Your branch is up to date with 'origin/8.19'.

You are currently cherry-picking commit 8f64c3ca.
  (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:   internal/beater/beater_test.go
	modified:   internal/beater/config/rum_test.go
	modified:   internal/beater/interceptors/metrics_test.go
	modified:   internal/beater/otlp/grpc_test.go
	modified:   internal/beater/request/context_test.go
	modified:   internal/publish/pub_test.go
	modified:   internal/sourcemap/elasticsearch_test.go
	modified:   internal/sourcemap/processor_test.go
	modified:   x-pack/apm-server/main_test.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   internal/agentcfg/cache_test.go

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? 🙏