binder: Move BinderTransport's inner classes to the top level (grpc#12303)

BinderTransport.java was getting too long and deeply nested.

This is a pure refactor with no behavior changes.

Author: jdcormie

binder/src/androidTest/java/io/grpc/binder/internal/BinderClientTransportTest.java

@@ -100,7 +100,7 @@ public final class BinderClientTransportTest {
           .build();
 
   AndroidComponentAddress serverAddress;
-  BinderTransport.BinderClientTransport transport;
+  BinderClientTransport transport;
   BlockingSecurityPolicy blockingSecurityPolicy = new BlockingSecurityPolicy();
 
   private final ObjectPool<ScheduledExecutorService> executorServicePool =
@@ -178,7 +178,7 @@ public BinderClientTransportBuilder setPreAuthorizeServer(boolean preAuthorizeSe
       return this;
     }
 
-    public BinderTransport.BinderClientTransport build() {
+    public BinderClientTransport build() {
       return factoryBuilder
           .buildClientTransportFactory()
           .newClientTransport(serverAddress, new ClientTransportOptions(), null);
@@ -502,8 +502,7 @@ public void testAsyncSecurityPolicyCancelledUponExternalTermination() throws Exc
   }
 
   private static void startAndAwaitReady(
-      BinderTransport.BinderClientTransport transport, TestTransportListener transportListener)
-      throws Exception {
+      BinderClientTransport transport, TestTransportListener transportListener) throws Exception {
     transport.start(transportListener).run();
     transportListener.awaitReady();
   }

binder/src/androidTest/java/io/grpc/binder/internal/BinderTransportTest.java

@@ -106,8 +106,7 @@ protected ManagedClientTransport newClientTransport(InternalServer server) {
     options.setEagAttributes(eagAttrs());
     options.setChannelLogger(transportLogger());
 
-    return new BinderTransport.BinderClientTransport(
-        builder.buildClientTransportFactory(), addr, options);
+    return new BinderClientTransport(builder.buildClientTransportFactory(), addr, options);
   }
 
   @Test

binder/src/main/java/io/grpc/binder/internal/ActiveTransportTracker.java

@@ -11,8 +11,8 @@
 import io.grpc.internal.ServerTransportListener;
 
 /**
- * Tracks which {@link BinderTransport.BinderServerTransport} are currently active and allows
- * invoking a {@link Runnable} only once all transports are terminated.
+ * Tracks which {@link BinderServerTransport} are currently active and allows invoking a {@link
+ * Runnable} only once all transports are terminated.
  */
 final class ActiveTransportTracker implements ServerListener {
   private final ServerListener delegate;