Istio 1.20 introduced Gateway API version 1.0. With that, we should upgrade the feature status to Generally Available.

This epic is to put in place any additional engineering, documentation and/or testing needed to declare this feature generally available so that it can be supported for the remainder of 2.x's lifecycle.

This includes, but is not limited to:

• OSSM operator installs "Gateway API" CRDs with a unique "GatewayClass"
• Configuration setting removes "techPreview" flag
• Add documentation for the above setting in Control plane configuration.
• Add documentation along side "Gateway Injection" for creating Gateways using Gateway API, taking into account the network policy changes needed (As noted in this slack thread on using Gateway API, that is a gotcha) The Sail operator doc on Gateway API is also relevant: https://github.com/maistra/istio-operator/blob/maistra-3.0/bundle/README.md#creating-and-configuring-gateways. 
• Decide if it is to be enabled by default - for now, no.
• Ensure we have ongoing QE testing covering the flag setting and the Gateway creation/usage. There could be other coverage - Gateway API's usage is not limited to gateways, but we should be able to mostly rely on upstream testing.

Note that this is a blocker for OSSM 2.6, because Gateway API is GA upstream, we need to also declare a comparable readiness for OSSM.