feat: Support for multiple rpc service generation and rpc grouping (#1972)

* Add group & compatible flag

* Add group & compatible flag

* Support for multiple rpc service generation and rpc grouping

* Support for multiple rpc service generation and rpc grouping

* Format code

* Format code

* Add comments

* Fix unit test

* Refactor function name

* Add example & Update grpc readme

* go mod tidy

* update mod

* update mod

tools/goctl/example/rpc/hi.proto

@@ -0,0 +1,33 @@
+syntax = "proto3";
+
+package hi;
+
+option go_package = "./hi";
+
+message HiReq {
+  string in = 1;
+}
+
+message HelloReq {
+  string in = 1;
+}
+
+message HiResp {
+  string msg = 1;
+}
+
+message HelloResp {
+  string msg = 1;
+}
+
+service Greet {
+  rpc SayHi(HiReq) returns (HiResp);
+  rpc SayHello(HelloReq) returns (HelloResp);
+}
+
+message EventReq{}
+message EventResp{}
+
+service Event {
+  rpc AskQuestion(EventReq) returns (EventResp);
+}