Implementable ProxySettingsPolicy proposal

[ciarams87]

Proposed changes

Problem: As a user of NGF
I want a design to configure NGINX's proxy buffer configuration for my applications through the use of ProxySettingsPolicy
So that I can implement the ProxySettingsPolicy CRD

Solution: Create an implementable ProxySettingsPolicy enhancement proposal

Testing: Describe any testing that you did.

Please focus on (optional): If you any specific areas where you would like reviewers to focus their attention or provide
specific feedback, add them here.

Closes #4067

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.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.08%. Comparing base (fc7806a) to head (d2aefe7).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4256      +/-   ##
==========================================
- Coverage   86.10%   86.08%   -0.03%     
==========================================
  Files         132      132              
  Lines       14342    14342              
  Branches       35       35              
==========================================
- Hits        12349    12346       -3     
- Misses       1790     1792       +2     
- Partials      203      204       +1     

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[bjee19]

nice