TUN-8052: Update go to 1.21.5

Also update golang.org/x/net and google.golang.org/grpc to fix vulnerabilities,
although cloudflared is using them in a way that is not exposed to those risks

vendor/google.golang.org/grpc/internal/experimental.go

@@ -0,0 +1,28 @@
+/*
+ * Copyright 2023 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package internal
+
+var (
+	// WithRecvBufferPool is implemented by the grpc package and returns a dial
+	// option to configure a shared buffer pool for a grpc.ClientConn.
+	WithRecvBufferPool any // func (grpc.SharedBufferPool) grpc.DialOption
+
+	// RecvBufferPool is implemented by the grpc package and returns a server
+	// option to configure a shared buffer pool for a grpc.Server.
+	RecvBufferPool any // func (grpc.SharedBufferPool) grpc.ServerOption
+)