fix: Working authClassName filter if multiple heimdall deployments are present in a cluster

[netthier]

Related issue(s)

closes #736

Checklist

• I agree to follow this project's Code of Conduct.
• I have read, and I am following this repository's Contributing Guidelines.
• I have read the Security Policy.
• I have referenced an issue describing the bug/feature request.
• I have added tests that prove the correctness of my implementation.
• I have updated the documentation.

Description

This PR fixes the issue mentioned above by moving the filtering logic into the creation, update and deletion functions.
It does make the code less DRY, but I've never written Go before so I'm unsure how to solve this more cleanly.
It furthermore also solves an issue where rewrites have to have all fields set, which is incorrect behavior.

It also contains fixes to make the DNS resolution tests pass more reliably

Changelist

fix: Fix authClassName filtering
fix: Make DNS resolution tests pass more reliably
fix: Allow rewrites with only a subset of fields set

[codecov]

Codecov Report

Merging #742 (958c724) into main (dff3d4d) will decrease coverage by 0.15%.
The diff coverage is 44.00%.

@@            Coverage Diff             @@
##             main     #742      +/-   ##
==========================================
- Coverage   89.59%   89.45%   -0.15%     
==========================================
  Files         215      215              
  Lines        9229     9238       +9     
==========================================
- Hits         8269     8264       -5     
- Misses        767      779      +12     
- Partials      193      195       +2     

Impacted Files	Coverage Δ
internal/rules/provider/kubernetes/provider.go	81.81% <36.36%> (-6.95%)	⬇️
internal/rules/rule_factory_impl.go	97.09% <100.00%> (ø)

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[dadrus]

I'm merging it as is and going to create another PR with some test for the given fixes