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/hello/client/greet/greet.go

@@ -0,0 +1,37 @@
+// Code generated by goctl. DO NOT EDIT!
+// Source: hello.proto
+
+package client
+
+import (
+	"context"
+
+	"github.com/zeromicro/go-zero/tools/goctl/example/rpc/hello/pb/hello"
+
+	"github.com/zeromicro/go-zero/zrpc"
+	"google.golang.org/grpc"
+)
+
+type (
+	HelloReq  = hello.HelloReq
+	HelloResp = hello.HelloResp
+
+	Greet interface {
+		SayHello(ctx context.Context, in *HelloReq, opts ...grpc.CallOption) (*HelloResp, error)
+	}
+
+	defaultGreet struct {
+		cli zrpc.Client
+	}
+)
+
+func NewGreet(cli zrpc.Client) Greet {
+	return &defaultGreet{
+		cli: cli,
+	}
+}
+
+func (m *defaultGreet) SayHello(ctx context.Context, in *HelloReq, opts ...grpc.CallOption) (*HelloResp, error) {
+	client := hello.NewGreetClient(m.cli.Conn())
+	return client.SayHello(ctx, in, opts...)
+}