Support appProtocol Field for HTTPBackendRef

[mpstefan]

As a user of NGF
I want appProtocol field to be supported for HTTPBackendRefs
So that I can ensure all traffic to my application is the protocol I expect.

Acceptance

• A BackendRef is marked as invalid if it refers to a Kubernetes Service that has an incompatible appProtocol for the given Route type.
• The "New Standard Protocols" as outlined in GEP-3726 are included:
  • 'kubernetes.io/h2c'
  • 'kubernetes.io/ws'
  • 'kubernetes.io/wss'
• If incoming traffic does not match the corresponding protocol, that traffic is rejected??