WIP: Restore cpu efficient cache

[mariomac]

Restore the CPU-efficient cache that was reverted in: #1362

This PR is still not ready to be merged. It introduced a memory leak that we haven't been yet able to manually reproduce and fix.

[codecov]

Codecov Report

Attention: Patch coverage is 93.75000% with 4 lines in your changes missing coverage. Please review.

Project coverage is 78.55%. Comparing base (d19600e) to head (9bc246a).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/kubecache/service/service.go	93.75%	3 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1379      +/-   ##
==========================================
+ Coverage   72.36%   78.55%   +6.18%     
==========================================
  Files         145      146       +1     
  Lines       14722    14767      +45     
==========================================
+ Hits        10654    11600     +946     
+ Misses       3359     2565     -794     
+ Partials      709      602     -107     

Flag	Coverage Δ
integration-test	?
k8s-integration-test	59.89% <75.00%> (-0.10%)	⬇️
oats-test	34.10% <ø> (ø)
unittests	51.98% <93.75%> (?)

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[mariomac]

Giving up with this approach.