fix: controller leader-election bug and cache-sync readiness

[jukie]

What this PR does / why we need it:

• Adds a more enhanced readiness check vs a healthz ping so that caches are synced before marking controller pods as ready
• Fixes a bug when setting up controller where leader election was disabled
• Enables controller warmup to allow non-leaders to pre-populate caches and keep them updated

Which issue(s) this PR fixes:

Fixes #7115

Release Notes: Yes

[codecov]

Codecov Report

❌ Patch coverage is 41.66667% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 72.35%. Comparing base (84672ca) to head (242815e).

Files with missing lines	Patch %	Lines
internal/provider/kubernetes/kubernetes.go	41.66%	5 Missing and 2 partials ⚠️

❌ Your patch check has failed because the patch coverage (41.66%) is below the target coverage (60.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7430      +/-   ##
==========================================
+ Coverage   72.31%   72.35%   +0.04%     
==========================================
  Files         231      231              
  Lines       34041    34051      +10     
==========================================
+ Hits        24617    24639      +22     
+ Misses       7645     7636       -9     
+ Partials     1779     1776       -3     

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[arkodg]

hey can we get more info from the users to confirm this is seen during EG restarts, and for a short duration, then this fix would make sense