Add support for custom environment variables on the Nginx Controller container

[AaronShiels]

Proposed changes

This pull request implements #3319.

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works*
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto main
• I will ensure my PR is targeting the main branch and pulling from my branch from my own fork

Note

No tests available for the Helm chart, but running the following command produces the desired results

helm template --debug nginx-ingress ./deployments/helm-chart --set controller.env[0].name=MY_VAR --set controller.env[0].value=myvalue > test.yaml

[codecov-commenter]

Codecov Report

Merging #3326 (a718f1d) into main (3637ddd) will increase coverage by 0.02%.
The diff coverage is 100.00%.

❗ Current head a718f1d differs from pull request most recent head 2b04323. Consider uploading reports for the commit 2b04323 to get more accurate results

@@            Coverage Diff             @@
##             main    #3326      +/-   ##
==========================================
+ Coverage   51.95%   51.98%   +0.02%     
==========================================
  Files          60       60              
  Lines       16797    16811      +14     
==========================================
+ Hits         8727     8739      +12     
  Misses       7775     7775              
- Partials      295      297       +2     

Impacted Files	Coverage Δ
internal/configs/version2/http.go	0.00% <ø> (ø)
pkg/apis/configuration/validation/policy.go	91.16% <ø> (ø)
internal/configs/virtualserver.go	95.07% <100.00%> (+0.01%)	⬆️
internal/k8s/configuration.go	95.43% <100.00%> (-0.34%)	⬇️
internal/k8s/validation.go	93.81% <100.00%> (ø)
...is/configuration/validation/globalconfiguration.go	88.33% <100.00%> (ø)
...g/apis/configuration/validation/transportserver.go	96.62% <100.00%> (ø)
pkg/apis/configuration/validation/virtualserver.go	94.39% <100.00%> (+<0.01%)	⬆️
...ternal/k8s/appprotect/app_protect_configuration.go	86.74% <0.00%> (+0.57%)	⬆️

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[shaun-nx]

Nice work with this @AaronShiels! 🚀