Gateway docstrings do not specify behavior for when request hostname does not match any listener hostname.

[briantkennedy]

What would you like to be added:

The GatewaySpec.Listener docstring does not define behavior for when a request does not match any hostname defined in a Listener.

Why this is needed:

The only place this is defined is in a single conformance test: https://github.com/kubernetes-sigs/gateway-api/blob/232953d038961461aaa5c21ad69a8138683d4e24/conformance/tests/httproute-listener-hostname-matching.go#L92