Fix informers on stale object deletion

[mariomac]

Some Beyla pods suddenly had an inusual memory generation, affecting also CPU due to constant garbage collections:

At the time the memory and garbage collection started to go mad, there is a log message like this:

W1128 10:31:37.371693       1 reflector.go:462] k8s.io/client-go/informers/factory.go:159: watch of *v1.Pod ended with: very short watch: k8s.io/client-go/informers/factory.go:159: Unexpected watch close - watch lasted less than a second and no items received

Followed by many log messages like:

E1128 10:32:21.406329       1 reflector.go:147] k8s.io/client-go/informers/factory.go:159: Failed to watch *v1.Pod: unable to sync list result: was expecting a *v1.Pod. Got: cache.DeletedFinalStateUnknown

This PR handles the cache.DeletedFinalStateUnknown event to delete anyway the object that is associated to it.

[marctc]

🤞

[codecov]

Codecov Report

Attention: Patch coverage is 54.34783% with 42 lines in your changes missing coverage. Please review.

Project coverage is 80.95%. Comparing base (77046c4) to head (6ed0631).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/kubecache/meta/informers_init.go	54.34%	39 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1420      +/-   ##
==========================================
+ Coverage   72.30%   80.95%   +8.64%     
==========================================
  Files         145      146       +1     
  Lines       14893    14925      +32     
==========================================
+ Hits        10768    12082    +1314     
+ Misses       3405     2256    -1149     
+ Partials      720      587     -133     

Flag	Coverage Δ
integration-test	58.98% <0.00%> (-0.14%)	⬇️
k8s-integration-test	60.06% <54.34%> (+0.02%)	⬆️
oats-test	33.97% <0.00%> (+<0.01%)	⬆️
unittests	51.57% <29.34%> (?)

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