Use custom ThreadFactory that does FastThreadLocal wrapping for us

This primarily has the benefit of not giving threads strange names

proxy/src/main/java/com/velocitypowered/proxy/network/TransportType.java

@@ -1,6 +1,6 @@
 package com.velocitypowered.proxy.network;
 
-import com.google.common.util.concurrent.ThreadFactoryBuilder;
+import com.velocitypowered.proxy.util.concurrent.VelocityNettyThreadFactory;
 import io.netty.channel.EventLoopGroup;
 import io.netty.channel.epoll.Epoll;
 import io.netty.channel.epoll.EpollDatagramChannel;
@@ -19,7 +19,6 @@ import io.netty.channel.socket.SocketChannel;
 import io.netty.channel.socket.nio.NioDatagramChannel;
 import io.netty.channel.socket.nio.NioServerSocketChannel;
 import io.netty.channel.socket.nio.NioSocketChannel;
-import io.netty.util.concurrent.DefaultThreadFactory;
 import java.util.concurrent.ThreadFactory;
 import java.util.function.BiFunction;
 
@@ -61,7 +60,7 @@ enum TransportType {
   }
 
   private static ThreadFactory createThreadFactory(final String name, final Type type) {
-    return new DefaultThreadFactory("Netty " + name + ' ' + type.toString(), false);
+    return new VelocityNettyThreadFactory("Netty " + name + ' ' + type.toString() + " #%d");
   }
 
   public static TransportType bestType() {

proxy/src/main/java/com/velocitypowered/proxy/util/concurrent/VelocityNettyThreadFactory.java

@@ -0,0 +1,23 @@
+package com.velocitypowered.proxy.util.concurrent;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import io.netty.util.concurrent.FastThreadLocalThread;
+import java.util.concurrent.ThreadFactory;
+import java.util.concurrent.atomic.AtomicInteger;
+
+public class VelocityNettyThreadFactory implements ThreadFactory {
+
+  private final AtomicInteger threadNumber = new AtomicInteger();
+  private final String nameFormat;
+
+  public VelocityNettyThreadFactory(String nameFormat) {
+    this.nameFormat = checkNotNull(nameFormat, "nameFormat");
+  }
+
+  @Override
+  public Thread newThread(Runnable r) {
+    String name = String.format(nameFormat, threadNumber.incrementAndGet());
+    return new FastThreadLocalThread(r, name);
+  }
+}