chore: refactor pod webhook mutator

[RealAnna]

This PR

makes some refactoring to prepare for kuttl tests implementation

• refactor pod mutator to reduce the complexity of the handler function

Related Issues

part of #391

[codecov]

Codecov Report

Merging #410 (e4587f5) into main (42f9b00) will increase coverage by 0.01%.
The diff coverage is 84.21%.

@@            Coverage Diff             @@
##             main     #410      +/-   ##
==========================================
+ Coverage   71.29%   71.31%   +0.01%     
==========================================
  Files          11       11              
  Lines         836      847      +11     
==========================================
+ Hits          596      604       +8     
- Misses        213      215       +2     
- Partials       27       28       +1     

Impacted Files	Coverage Δ
webhooks/pod_webhook.go	83.62% <84.21%> (-0.32%)	⬇️

Flag	Coverage Δ
component-tests	65.04% <84.21%> (+0.13%)	⬆️
unit-tests	20.77% <0.00%> (-0.28%)	⬇️

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[toddbaert]

I think these are good function extractions.