Update GatewayAPI to v1.4.0

[ciarams87]

Proposed changes

Problem: We don't currently support the latest version of the Gateway API

Solution: Upgrade to v1.4.0, including BackendTLSPolicy promotion -> v1 and other Policy type promotion -> v1. See the full changelog. Also enables the conformance tests for BackendTLSPolicy.

Testing: unit testing, running the pipeline for conformance and functional testing, but the RC run passed conformance.

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 #4034
Closes #3795

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.

Upgrade Gateway API to v1.4.0

[codecov]

Codecov Report

❌ Patch coverage is 69.64286% with 17 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.03%. Comparing base (1b34946) to head (00a8061).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/controller/state/conditions/conditions.go	0.00%	15 Missing ⚠️
internal/controller/state/graph/gatewayclass.go	60.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4166      +/-   ##
==========================================
+ Coverage   85.99%   86.03%   +0.03%     
==========================================
  Files         131      131              
  Lines       14063    14058       -5     
  Branches       35       35              
==========================================
+ Hits        12094    12095       +1     
+ Misses       1769     1763       -6     
  Partials      200      200              

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