gRPC client: Strip "grpc-go/version" suffix from User-Agent header (#5689)

Fixes https://github.com/XTLS/Xray-core/pull/5658#issuecomment-3894269376

---------

Co-authored-by: RPRX <63339210+RPRX@users.noreply.github.com>

transport/internet/grpc/config_test.go

@@ -1,9 +1,12 @@
 package grpc
 
 import (
+	"reflect"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials/insecure"
 )
 
 func TestConfig_GetServiceName(t *testing.T) {
@@ -115,3 +118,12 @@ func TestConfig_GetTunMultiStreamName(t *testing.T) {
 		})
 	}
 }
+
+func TestSetUserAgent(t *testing.T) {
+	ua := "Test/1.0"
+	conn, err := grpc.NewClient("localhost:50051", grpc.WithTransportCredentials(insecure.NewCredentials()), grpc.WithUserAgent(ua))
+	assert.NoError(t, err)
+	defer conn.Close()
+	setUserAgent(conn, ua)
+	assert.Equal(t, ua, reflect.ValueOf(conn).Elem().FieldByName("dopts").FieldByName("copts").FieldByName("UserAgent").String())
+}