UDP support in Consul Connect

#### Feature Description

allow specifying UDP as the protocol when setting up consul connect, which then can be used for one way UDP communication between services (metrics sink for example).

#### Use Case(s)

As stated here: https://github.com/hashicorp/nomad/issues/9161#issuecomment-716550628, there is no easy way right now to setup UDP communication between services in the mesh at the moment. Allow UDP will make sending metrics from one service to another within service mesh on nomad a lot easier.

Although not related to my use case, there are some discussion about udp support in istio: https://github.com/istio/istio/issues/1430. Not sure if they are relevant/applicable in the context of Consul Connect.