Add nginx image version validation during agent connections

[salonichf5]

Cherry pick for PR

Closes #3867

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

Release notes

If this PR introduces a change that affects users and needs to be mentioned in the release notes,
please add a brief note that summarizes the change.

Added nginx image version validation during agent connections to prevent newer config being sent to pods running previous image versions during upgrades

[codecov]

Codecov Report

❌ Patch coverage is 87.65432% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.91%. Comparing base (1d3ce3a) to head (77b478d).
⚠️ Report is 1 commits behind head on release-2.1.

Files with missing lines	Patch %	Lines
internal/controller/nginx/agent/command.go	75.60%	8 Missing and 2 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##           release-2.1    #3953   +/-   ##
============================================
  Coverage        86.91%   86.91%           
============================================
  Files              128      128           
  Lines            16013    16059   +46     
  Branches            62       62           
============================================
+ Hits             13918    13958   +40     
- Misses            1926     1931    +5     
- Partials           169      170    +1     

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