#2982 provided basic HTTP gateway implementation, but several pieces are missing.

things that can be built w/ v1 apis

• when the backing service has more than one port
• when the route rule applies to a particular ingress port
• when the route has wildcard hostnames
• when the gateway has wildcard hostnames (prefix wildcard complete, see Gateway hosts may contain wildcards #3634)

things that need a conversation

• workload-selectors (if the gateway isn't running any service instances, where do the labels come from?)

things that probably need envoy v2 apis

• non-HTTP listeners
• merging gateways with different TLS config

cc: @rosenhouse @rshriram @ZackButcher