Add initial zone_sync values to the ConfigMap

[AlexFenlon]

Proposed changes

This pr adds the following zone_sync values to the default nginx-config ConfigMap.

• zone-sync true/false
• zone-sync-port - int

zone-sync-port requires zone-sync to be enabled, which in turn needs NGINX Plus enabled.

Domain is also added and is written dynamically based on the namespace of the controller eg.
nginx-ingress-headless.nginx-ingress.svc.cluster.local

This PR only just adds the values and the validation for it, the user cannot enter anyhing until future implementation.
Resolves: #7218

apiVersion: v1
kind: ConfigMap
metadata:
  name: nginx-config
  namespace: nginx-ingress
data:
  zone-sync: true
  zone-sync-port: 1234

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

[codecov]

Codecov Report

Attention: Patch coverage is 62.79070% with 16 lines in your changes missing coverage. Please review.

Project coverage is 52.74%. Comparing base (3f73934) to head (2b32f83).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/configs/configmaps.go	62.79%	11 Missing and 5 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7239      +/-   ##
==========================================
+ Coverage   52.72%   52.74%   +0.02%     
==========================================
  Files          89       89              
  Lines       20843    20886      +43     
==========================================
+ Hits        10989    11016      +27     
- Misses       9396     9407      +11     
- Partials      458      463       +5     

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[shaun-nx]

@AlexFenlon Just a heads up, we will need to update our ConfigMap keys in confluence with this new setting. This doesn't have to do in this PR, but just to make sure it's captured

[javorszky]

Approved with questions around naming things.