Update GatewayAPI to v1.4.0

[ciarams87]

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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.

This also requires upgrading the inference extension from 1.0.2 -> 1.1.0 to resolve dependency conflicts.

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.

• [x] I have read the CONTRIBUTING doc
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] I have checked that all unit tests pass after adding my changes
• [ ] I have updated necessary documentation
• [x] 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