move lock/unlock implementaion outside of Surface into SurfaceTextureClient

This makes ANativeWindow_lock/ANativeWindow_unlockAndPost work
with ANativeWindows implemented by Surface and SurfaceTextureClient.

Also, Surface now inherits directly from SurfaceTextureClient.

Bug: 5003724
Change-Id: I9f285877c7bae9a262e9a7af91c2bae78804b2ef