[DNM] Use upstream gateway-api types

[adleong]

This change removes our dependency on the hand-rolled kubernetes gateway API bindings from the k8s-gateway-api crate and replaces them with the official generated bindings from the gateway-api crate.

This change is in progress and at this time does not yet compile and requires polish and import naming consistency improvements.

[olix0r]

Note that you do not necessarily need to expose this as a pure re-export. You can potentially avoid changing many type signatures by providing some consistent naming between versions.

This might look something like:

pub mod gateway {
    pub use gateway_api::apis::experimental::{
        httproutes::*,
        grpcroutes::*,
        tlsroutes::*,
    };
}

This would preserve references to k8s_gateway_api::GrpcRoute as they were before (avoiding the change to k8s_gateway_api::grpcroutes::GrpcRoute)

Furthermore, you could potentially use this approach to front-load some type naming changes before updating the crate version.

For example, we could stage out some of the changes with:

pub mod gateway {
    pub use k8s_gateway_api::*;

    pub type HTTPRouteStatus = k8s_gateway_api::RouteStatus;
    // etc... 
}