Changes to improve reliability of token monitor

[caseydavenport]

Description

We've seen a few issues where it looks like our token monitor isn't spotting that the token changes. This is meant to try to improve the reliability of the monitor by:

• Monitoring files direcly, in addition to the directory
• Adding a backstop in the form of a periodic resync.

Related issues/PRs

Related to #4857

Todos

• Tests
• Documentation
• Release note

Release Note

Improve reliability of token monitor

[hopefulwalker]

This improvement was released？
I hit the problem. I'm using two environment which build by the same ansible scripts.

1. one installation, calico/node has logs about token refresh,
2. the other one has no logs, so after 24 hours, the token was invalidated, I have to delete the pods(calico/node), it work again.
   I have no idea about how to solved it. and try to set CALICO_MANAGE_CNI=true.

[hopefulwalker]

My way to install calico is

1. https://projectcalico.docs.tigera.io/getting-started/kubernetes/self-managed-onprem/onpremises
2. kubectl apply manifests file: https://raw.githubusercontent.com/projectcalico/calico/v3.24.5/manifests/calico.yaml
3. That's it.
   Everything is fine, except the token monitor doesn't work.

[caseydavenport]

We ended up going a different direction so the changes in this PR weren't needed. I'd recommend opening an issue to track discussion of the problems you're seeing in your cluster