fix(operator): Changed checks on pod owner replicas

[RealAnna]

This PR fixes #379 :

• In case the pod is under a replica set or a stateful set we should check that the available replicas correspond to the wanted replicas, not try to retrieve the deployment
• adds tests
• refactor namespace usage in kuttl tests

[codecov]

Codecov Report

Merging #412 (d61a3a6) into main (df346f7) will increase coverage by 1.29%.
The diff coverage is 69.56%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #412      +/-   ##
==========================================
+ Coverage   26.15%   27.44%   +1.29%     
==========================================
  Files          16       16              
  Lines        1495     1483      -12     
==========================================
+ Hits          391      407      +16     
+ Misses       1086     1056      -30     
- Partials       18       20       +2     

Impacted Files	Coverage Δ
operator/webhooks/pod_mutating_webhook.go	36.22% <0.00%> (ø)
...keptnworkloadinstance/reconcile_deploymentstate.go	40.00% <72.72%> (+28.88%)	⬆️

Flag	Coverage Δ
keptn-lifecycle-operator	31.45% <69.56%> (+1.55%)	⬆️
scheduler	4.52% <ø> (ø)

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