What would you like to be added: support for port matching in routes

Why this is needed:

Mesh (primary use case): for mesh, we are using a parentRef of Mesh, instead of Gateway. As such, there is no port matching available, since we do not get ports in the Gateway.listener like we do with Gateway cases. Matching on ports is quite common in mesh; for example, if I am defining some policy for google.com, I know I only need this for port 80 since google isn't serve on 8080.
Ingress (secondary use case): This is similar to hostname attachment in many ways. Rather than requiring a bunch of sectionNames, I want to attach to multiple sections at once by filtering by port instead of explicit listener reference

Prior art: https://istio.io/latest/docs/reference/config/networking/virtual-service/#HTTPMatchRequest has a port field

Design ideas:

• Add it to TrafficMatches from GEP 735 L4 Traffic Matching #932. This only applies to TCP/UDP route though; we would need this in HTTP and TLS as well
• Use sectionName (ie sectionName: "80"). This would work but is a bit odd since port is a string here. Would only apply to mesh
• Add a new port field to parentRef. For Gateway, this would act as an additional filter on listeners bound. For mesh, this would scope to that port.