Add configuration options to Kube Cache service

[mariomac]

Prior to dogfooding, this PR adds some extra configuration options to the service.

[codecov]

Codecov Report

Attention: Patch coverage is 40.98361% with 36 lines in your changes missing coverage. Please review.

Project coverage is 80.45%. Comparing base (916fd95) to head (0ea41b8).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
cmd/k8s-cache/main.go	39.02%	19 Missing and 6 partials ⚠️
pkg/kubecache/config.go	21.42%	9 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1304      +/-   ##
==========================================
- Coverage   80.54%   80.45%   -0.10%     
==========================================
  Files         141      142       +1     
  Lines       14217    14262      +45     
==========================================
+ Hits        11451    11474      +23     
- Misses       2225     2242      +17     
- Partials      541      546       +5     

Flag	Coverage Δ
integration-test	58.75% <ø> (-0.03%)	⬇️
k8s-integration-test	58.38% <40.98%> (-0.06%)	⬇️
oats-test	35.01% <ø> (-0.01%)	⬇️
unittests	52.44% <9.83%> (-0.16%)	⬇️

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[grcevski]

LGTM!