proxy: use grpc interfaces instead of *grpc.Server and *grpc.ClientConn, use Service and service Options

Signed-off-by: Adphi <philippe.adrien.nousse@gmail.com>

proxy/testservice/test_vtproto.pb.go

@@ -6,9 +6,10 @@ package testservice
 
 import (
 	fmt "fmt"
+	io "io"
+
 	protohelpers "github.com/planetscale/vtprotobuf/protohelpers"
 	protoimpl "google.golang.org/protobuf/runtime/protoimpl"
-	io "io"
 )
 
 const (