Upgrade Gateway API to v1.1.0

[ciarams87]

Proposed changes

Problem: We don't support the latest version of the Gateway API (v1.1.0)

Solution: Upgrade to the latest version. As part of this upgrade, we must/ can:

• Upgrade BackendTLSPolicy to v1alpha3 (breaking change, required)
• Upgrade GRPCRoute to v1 (this means it does not need to be behind the experimental flag, and we don't need to support v1alpha2 of the API)
• Enable the GRPCRoute Conformance tests
• PolicyTargetReference has been removed, so use LocalPolicyTargetReference for the target refs in our new policies (can optionally use NamespacedPolicyTargetReference instead, but we already have the requirement of the targets being in the same namespace as the policies)
• Fix the conformance tests to run on the latest version, which also means the main Gateway API branch in the nightly run is fixed

Testing: Ran the full conformance test suite, including the GRPCRoute tests. Locally tested the BackendTLSPolicy workflow following the guide.

Closes #1970

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.

Updated to v1.1.0 of the Gateway API. This includes a breaking change to BackendTLSPolicies - see [the release notes](https://github.com/kubernetes-sigs/gateway-api/releases/tag/v1.1.0) for further details

[codecov]

Codecov Report

Attention: Patch coverage is 97.18310% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 87.03%. Comparing base (aa16231) to head (7839f55).

Files	Patch %	Lines
internal/mode/provisioner/manager.go	0.00%	1 Missing ⚠️
internal/mode/static/manager.go	83.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1975      +/-   ##
==========================================
+ Coverage   86.98%   87.03%   +0.04%     
==========================================
  Files          89       89              
  Lines        6091     6091              
  Branches       50       50              
==========================================
+ Hits         5298     5301       +3     
+ Misses        741      737       -4     
- Partials       52       53       +1     

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[kate-osborn]

LGTM

[sjberman]

Table on our top-level README also needs to be updated

[ADubhlaoich]

LGTM docs-wise!