feat: implement client to send FinalizeCleanup requests to spectro-cleanup

[ahmad-ibra]

Implements a client for invoking the FinalizeCleanup endpoint of spectro-cleanup:
https://buf.build/spectrocloud/spectro-cleanup/docs/main:cleanup.v1

[codecov]

Codecov Report

Merging #155 (c7255a1) into main (1e340c9) will increase coverage by 1.20%.
The diff coverage is 88.23%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #155      +/-   ##
==========================================
+ Coverage   55.49%   56.69%   +1.20%     
==========================================
  Files           9        9              
  Lines         856      889      +33     
==========================================
+ Hits          475      504      +29     
- Misses        354      357       +3     
- Partials       27       28       +1     

Files	Coverage Δ
internal/controller/validatorconfig_controller.go	77.13% <88.23%> (+1.57%)	⬆️

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[TylerGillson]

Low priority, but it would be nice if the CLEANUP_GRPC_SERVER_X vars were exported from the spectro cleanup repo.