Add a loadBalancingMethod field to the Upstream Settings Policy API

[salonichf5]

Proposed changes

Write a clear and concise description that helps reviewers understand the purpose and impact of your changes. Use the
following format:

Problem: Users want to specify load balancing method via Upstream Settings Policy API

Solution: Extend Upstream settings policy API to support load balancing method field.

Testing: Manual testing applying CRDs

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 #4229

Checklist

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• 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.

Add a `loadBalancingMethod` field to the Upstream Settings Policy API 

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.13%. Comparing base (9d2bf35) to head (6fa5e7d).
⚠️ Report is 1 commits behind head on feat/session-persistence.

Additional details and impacted files

@@                     Coverage Diff                      @@
##           feat/session-persistence    #4251      +/-   ##
============================================================
+ Coverage                     86.11%   86.13%   +0.01%     
============================================================
  Files                           131      131              
  Lines                         14205    14205              
  Branches                         35       35              
============================================================
+ Hits                          12233    12235       +2     
+ Misses                         1768     1766       -2     
  Partials                        204      204              

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[sjberman]

Would you mind updating the PR title to be more descriptive about what you're actually updating?