Add TCPRoute and UDPRoute to Support L4 LoadBalancing

[Skcey]

In the project, there are plans to support TCPRoute and UDPRoute in the future. Building on this, I have supplemented the basic functionalities of TCPRoute and UDPRoute by referring to the implementations of HTTPRoute and TLSRoute.
Specifically, I added relevant controllers, implemented the corresponding route construction functions, and supplemented the generation of stream configurations, thereby enabling NGF to support TCPRoute and UDPRoute. This allows for simple Layer 4 load balancing, with each route supporting one listener. Currently, only one backend service is supported in the route.

[sjberman]

@Skcey Thanks for your interest. Is this a use case that you require? Trying to understand the priority here, so we can determine if we want to be able to support the full route solutions (i.e. multiple listeners/backends) before accepting the work, versus getting the minimal functionality in place to support a customer use case.

[mpstefan]

To add onto to this, I think in either case, we'd want an implementation for these two route to, at minimum, support all features listed as "core" in the spec:

TCPRoute
UDPRoute

I wouldn't want to release a feature for users who may start implementing this in a production environment only to find out it has restrictions that do not even reach core support.

It is great to see this PR, and if you're open to a little more work, we can definitely help you get it across the line!

[Skcey]

Thank you for your replies. I will continue to improve the function in the future.

[Skcey]

Currently, this requirement stems from my need to migrate from Ingress to Gateway API. The Layer 4 routing functionality that I've been able to implement with NGINX Ingress should also be achievable when switching to NGF later on. For now, I aim to simply complete the basic support for Layer 4 routing in NGF, and will continue to improve the features related to multiple listeners and multiple backends in subsequent phases.