Initial InputMappers for evdev input HAL.

The previous design of the InputHost wrapper classes made it very
painful to do testing, so this change also reverts to a more classical
C++ pattern for non-copyable objects. The InputHost classes still simply
call through to the input_host_t and callbacks as before.

Updated unittests to use gmock for mocking the InputHost interactions.

Change-Id: I4b70df2c89ed48af77446b8f5b87a4bde94510bf

modules/input/evdev/InputDeviceManager.cpp

@@ -43,7 +43,8 @@ void InputDeviceManager::onDeviceRemoved(const std::shared_ptr<InputDeviceNode>&
         return;
     }
     // TODO: tell the InputDevice and InputDeviceNode that they are being
-    // removed so they can run any cleanup.
+    // removed so they can run any cleanup, including unregistering from the
+    // host.
     mDevices.erase(node);
 }