Improve flannel RBAC changes

[brandond]

Proposed Changes

Only wait for k3s-controller RBAC when AuthorizeNodeWithSelectors blocks kubelet from listing nodes.

This allows agents to use whichever client allows flannel to list/watch nodes. If the feature-gate does not block access to nodes, then the kubelet kubeconfig will be used as in older releases. If it does block access, then we will wait for k3s-controller RBAC to be created and use that instead.

This is a forward-port of the compat changes being made to the <= v1.31 branches, where agents will need to support servers that may or may not have the updated k3s-controller RBAC.

Types of Changes

compat fix

Verification

see compat tests in CI

Testing

yes

Linked Issues

User-Facing Change

Further Comments

[codecov]

Codecov Report

Attention: Patch coverage is 47.05882% with 18 lines in your changes missing coverage. Please review.

Project coverage is 47.80%. Comparing base (0144d9b) to head (49148c8).
Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
pkg/util/api.go	40.00%	8 Missing and 4 partials ⚠️
pkg/agent/flannel/setup.go	57.14%	3 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #11569      +/-   ##
==========================================
- Coverage   50.04%   47.80%   -2.25%     
==========================================
  Files         185      185              
  Lines       19239    19265      +26     
==========================================
- Hits         9629     9209     -420     
- Misses       8222     8727     +505     
+ Partials     1388     1329      -59     

Flag	Coverage Δ
e2etests	40.58% <47.05%> (-3.74%)	⬇️
inttests	35.08% <47.05%> (-0.13%)	⬇️
unittests	17.03% <0.00%> (-0.03%)	⬇️

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