Rework consumer sample deletion when a channel is closed (backport #10476)

[mergify]

This is an automatic backport of pull request #10476 done by Mergify.
Cherry-pick of a2ff5a0 has failed:

On branch mergify/bp/v3.12.x/pr-10476
Your branch is up to date with 'origin/v3.12.x'.

You are currently cherry-picking commit a2ff5a0b7b.
  (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:   deps/rabbitmq_management_agent/src/rabbit_mgmt_metrics_gc.erl

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   deps/rabbit/src/rabbit_channel.erl

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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[michaelklishin]

The failing suite is now cached by BuildBuddy :/ and has nothing to do with this change.