feat(controller): make token cache ttl more dynamic

[krancour]

Supersedes #5615

In many cases, though not all, we have access to a token's expiry date/time.

For such cases, it is safer to derive cache TTL durations from the expiry than to make assumptions about how long the token is valid for.

This also adds debug level logging with details of token expiry (if known) and corresponding cache entry TTL.

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[codecov]

Codecov Report

❌ Patch coverage is 73.79310% with 38 lines in your changes missing coverage. Please review.
✅ Project coverage is 56.24%. Comparing base (cfad6be) to head (85adb9f).
⚠️ Report is 8 commits behind head on main.

Files with missing lines	Patch %	Lines
...kg/credentials/gar/workload_identity_federation.go	66.66%	10 Missing ⚠️
pkg/credentials/ecr/managed_identity.go	66.66%	9 Missing ⚠️
pkg/credentials/ecr/access_key.go	69.23%	8 Missing ⚠️
pkg/credentials/github/app.go	76.92%	6 Missing ⚠️
pkg/credentials/gar/service_account_key.go	80.00%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5684      +/-   ##
==========================================
+ Coverage   56.15%   56.24%   +0.09%     
==========================================
  Files         448      448              
  Lines       37656    37759     +103     
==========================================
+ Hits        21145    21239      +94     
- Misses      15253    15263      +10     
+ Partials     1258     1257       -1     

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[hiddeco]

We are doing this in multiple places, probably better to extract it to a helper:

func CalculateCacheTTL(expiry time.Time, margin time.Duration) time.Duration {}