[Swift] Moves grpc example to grpc/examples (#6479)

Updates generated Code

Removes grpc generation code from tests dir

Small fix to generate.sh

grpc/examples/swift/Greeter/Sources/server/main.swift

@@ -0,0 +1,90 @@
+/*
+ * Copyright 2021 Google Inc. All rights reserved.
+ *
+ * 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.
+ */
+
+import FlatBuffers
+import GRPC
+import Logging
+import Model
+import NIO
+
+class Greeter: models_GreeterProvider {
+
+  var interceptors: models_GreeterServerInterceptorFactoryProtocol?
+
+  let greetings: [String]
+
+  init() {
+    greetings = ["Hi", "Hallo", "Ciao"]
+  }
+
+  func SayHello(
+    request: Message<models_HelloRequest>,
+    context: StatusOnlyCallContext) -> EventLoopFuture<Message<models_HelloReply>>
+  {
+    let recipient = request.object.name ?? "Stranger"
+
+    var builder = FlatBufferBuilder()
+    let off = builder.create(string: "Hello \(recipient)")
+    let root = models_HelloReply.createHelloReply(&builder, messageOffset: off)
+    builder.finish(offset: root)
+    return context.eventLoop.makeSucceededFuture(Message<models_HelloReply>(builder: &builder))
+  }
+
+  func SayManyHellos(
+    request: Message<models_HelloRequest>,
+    context: StreamingResponseCallContext<Message<models_HelloReply>>) -> EventLoopFuture<GRPCStatus>
+  {
+    for name in greetings {
+      var builder = FlatBufferBuilder()
+      let off = builder.create(string: "\(name) \(request.object.name ?? "Unknown")")
+      let root = models_HelloReply.createHelloReply(&builder, messageOffset: off)
+      builder.finish(offset: root)
+      _ = context.sendResponse(Message<models_HelloReply>(builder: &builder))
+    }
+    return context.eventLoop.makeSucceededFuture(.ok)
+  }
+}
+
+// Quieten the logs.
+LoggingSystem.bootstrap {
+  var handler = StreamLogHandler.standardOutput(label: $0)
+  handler.logLevel = .critical
+  return handler
+}
+
+let group = MultiThreadedEventLoopGroup(numberOfThreads: 1)
+defer {
+  try! group.syncShutdownGracefully()
+}
+
+// Create some configuration for the server:
+let configuration = Server.Configuration(
+  target: .hostAndPort("localhost", 0),
+  eventLoopGroup: group,
+  serviceProviders: [Greeter()])
+
+// Start the server and print its address once it has started.
+let server = Server.start(configuration: configuration)
+server.map {
+  $0.channel.localAddress
+}.whenSuccess { address in
+  print("server started on port \(address!.port!)")
+}
+
+// Wait on the server's `onClose` future to stop the program from exiting.
+_ = try server.flatMap {
+  $0.onClose
+}.wait()