- Fork the default `dns` resolver from `go-grpc` to add backend discovery via
DNS SRV resource records.
- Add new fields for SRV based discovery to `cmd.GRPCClientConfig`
- Add new (optional) field `DNSAuthority` for specifying custom DNS server to
`cmd.GRPCClientConfig`
- Add a utility method to `cmd.GRPCClientConfig` to simplify target URI and host
construction. With three schemes and `DNSAuthority` it makes more sense to
handle all of this parsing and construction outside of the RPC client
constructor.
Resolves#6111
Samantha