Warn about unhandled arguments

[jsoref]

Proposed changes

I was trying to use the ingress binary and unfortunately gave it the wrong first argument. Because of how flag.Parse() works, all of the arguments were ignored and the error I got was very confusing.

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-commenter]

Codecov Report

Merging #2641 (1d4991c) into main (420aa9a) will decrease coverage by 0.02%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main    #2641      +/-   ##
==========================================
- Coverage   53.44%   53.41%   -0.03%     
==========================================
  Files          52       52              
  Lines       14702    14706       +4     
==========================================
- Hits         7857     7855       -2     
- Misses       6585     6589       +4     
- Partials      260      262       +2     

Impacted Files	Coverage Δ
cmd/nginx-ingress/main.go	6.81% <0.00%> (-0.05%)	⬇️
internal/k8s/configuration.go	95.47% <0.00%> (-0.39%)	⬇️
...ternal/k8s/appprotect/app_protect_configuration.go	86.74% <0.00%> (+0.57%)	⬆️

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[lucacome]

Merging this, thanks @jsoref !