Revert "Add metrics to measure latency of k8s informer (#1200)"

[marctc]

This reverts commit 6960d77c4043220eaafe617f52a2d6a9a805ef14.

These metrics are not accurate as they are using Pod creation time as reference. The idea was to track latency of informers but the approach is not correct.

Alternatively we could have a counter, which would track how many times the handlers of an informer are called, but I don't think that's very useful.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 53.33333% with 7 lines in your changes missing coverage. Please review.

Project coverage is 81.79%. Comparing base (5cb7064) to head (7cc0dbf).

Files with missing lines	Patch %	Lines
pkg/internal/imetrics/imetrics.go	44.44%	5 Missing :warning:
pkg/internal/appolly/appolly.go	0.00%	0 Missing and 1 partial :warning:
pkg/internal/imetrics/iprom.go	50.00%	1 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1214      +/-   ##
==========================================
+ Coverage   81.76%   81.79%   +0.03%     
==========================================
  Files         137      137              
  Lines       11509    11465      -44     
==========================================
- Hits         9410     9378      -32     
+ Misses       1562     1547      -15     
- Partials      537      540       +3     

Flag	Coverage Δ
integration-test	60.91% <33.33%> (+0.49%)	:arrow_up:
k8s-integration-test	58.29% <53.33%> (-0.18%)	:arrow_down:
oats-test	36.28% <26.66%> (+0.13%)	:arrow_up:
unittests	53.10% <13.33%> (+0.15%)	:arrow_up:

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