Gateway API Beta support

[cgrotz]

Describe the feature

At the moment Gateway API Alpha is supported, since Juli Beta is released and Alpha is deprecated link At the moment on GKE Flagger fails with:

Internal error occurred: failed calling webhook "gateway-api-alpha-deprecated-use-beta-version.gke.io": failed to call webhook: Post "https://gateway-api-alpha-deprecated-use-beta-version.kube-system.svc:443/?timeout=1s": service "gateway-api-alpha-deprecated-use-beta-version" not found while reconciling

Proposed solution

Add support for Gateway API Beta

[stefanprodan]

Gateway API v1beta1 is our top priority, hopefully we’ll release it in the next few weeks. cc @aryan9600

[cgrotz]

I raised a pull request for this, but I have some problems regarding code generation.

[cgrotz]

I fixed the problems, would be great if somebody could take a look and give some C&C