Backport of fix(control-plane): acl tokens deleted while pods in graceful shutdown into release/1.4.x

[hc-github-team-consul-core]

Backport

This PR is auto-generated from #3736 to be assessed for backporting due to the inclusion of the label backport/1.4.x.

The below text is copied from the body of the original PR.

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Changes proposed in this PR

• Users have reported that when GracefulShutdown is enabled, ACL tokens are deleted immediately when a pod goes in to TERMINATING, which can disrupt consul DNS and an app's shutdown procedure if that is required.
• The new behavior is that if a pod still exists and has GracefulShutdown enabled, we will skip ACL and node cleanup, instead re-queue the event for the longest shutdown period, plus some buffer to cut down on noise.

How I've tested this PR

• Manual testing in a local kube cluster, deploying an app w/ ACLs and graceful shutdown. I delete a pod and watch the control-plane and consul-dataplane logs to verify when the ACL token is cleaned up.
• Additional unit tests added.

How I expect reviewers to test this PR

👀 ☕

Checklist

• Tests added
• CHANGELOG entry added

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Overview of commits

• 4a7cfeb

[DanStough]

No changes to this PR from the original.