chore: use sets.Set[T] instead of map[T]struct{}

[zirain]

fixes: #3411

[codecov]

Codecov Report

Attention: Patch coverage is 70.49180% with 18 lines in your changes are missing coverage. Please review.

Project coverage is 67.06%. Comparing base (c348370) to head (91a0897).

Files	Patch %	Lines
internal/provider/kubernetes/controller.go	40.90%	13 Missing ⚠️
internal/provider/kubernetes/routes.go	84.37%	0 Missing and 5 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3471      +/-   ##
==========================================
- Coverage   67.09%   67.06%   -0.03%     
==========================================
  Files         166      166              
  Lines       19618    19623       +5     
==========================================
- Hits        13163    13161       -2     
- Misses       5504     5509       +5     
- Partials      951      953       +2     

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[arkodg]

LGTM thanks !