Update the ThreadLocal based scopes to use RequestContext.

Bound the ThreadLocalRequestContext module, which makes the CurrentUser
available in the Global module. Removed any binding in the scopes that
provided the CurrentUser. Updated all of the scopes to propagate the
RequestContext. The PerThreadRequestScope.Propagator allows scoping
callables to enter a request context.

Change-Id: Idf682ed1d7485cf8c9cdd22cd89bfe1ad5296880

gerrit-sshd/src/main/java/com/google/gerrit/sshd/SshModule.java

@@ -152,11 +152,6 @@ public class SshModule extends FactoryModule {
     bind(SocketAddress.class).annotatedWith(RemotePeer.class).toProvider(
         SshRemotePeerProvider.class).in(SshScope.REQUEST);
 
-    bind(CurrentUser.class).toProvider(SshCurrentUserProvider.class).in(
-        SshScope.REQUEST);
-    bind(IdentifiedUser.class).toProvider(SshIdentifiedUserProvider.class).in(
-        SshScope.REQUEST);
-
     bind(WorkQueue.Executor.class).annotatedWith(CommandExecutor.class)
         .toProvider(CommandExecutorProvider.class).in(SshScope.REQUEST);