Kube meta store: Make sure all the object metadata is deleted

[mariomac]

I detected a memory leak in some Beyla instances even when they don't run the informers code.

Pyroscope points to Store.deleteObjectMeta as a source of memory growth:

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.00%. Comparing base (c4244b1) to head (5e4f425).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1359      +/-   ##
==========================================
+ Coverage   79.06%   81.00%   +1.94%     
==========================================
  Files         145      145              
  Lines       14648    14655       +7     
==========================================
+ Hits        11581    11871     +290     
+ Misses       2489     2210     -279     
+ Partials      578      574       -4     

Flag	Coverage Δ
integration-test	58.97% <0.00%> (+0.07%)	⬆️
k8s-integration-test	59.54% <100.00%> (+0.15%)	⬆️
oats-test	34.36% <0.00%> (?)
unittests	52.11% <100.00%> (+0.02%)	⬆️

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