terraform: enable build tag (backport #13841)

[mergify]

Motivation/summary

I'd like to honour the CI details so we can tag any cloud resources with the Build ID or so, this will help to identify if the resources were created when running the terraform locally or in the CI.

For instance, currently

Then when https://github.com/elastic/apm-aws-lambda/actions/workflows/smoke-tests.yml runs I wanna see

Or something similar

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 #13841 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of b4c79b3 has failed:

On branch mergify/bp/8.15/pr-13841
Your branch is up to date with 'origin/8.15'.

You are currently cherry-picking commit b4c79b3ab.
  (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:   testing/infra/terraform/modules/tags/README.md
	modified:   testing/infra/terraform/modules/tags/vars.tf

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   testing/infra/terraform/modules/tags/output.tf

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

[inge4pres]

LGTM 👍🏼 thanks

[endorama]

Oh, the cherry picked commit is not signed 😢 Fixing it

[kruskall]

@Mergifyio queue

[mergify]

queue

✅ The pull request has been merged automatically

The pull request has been merged automatically at 183a008

[kruskall]

@endorama mergify is special 😉