TextureView: add setSurfaceTexture method

This change adds support for transferring control of a TextureView's
SurfaceTexture between the UI framework and the application.  It makes the
TextureView detach the SurfaceTexture from the UI framework's GLES context
before calling the surfaceTextureDestroyed callback, allowing the app to use
the SurfaceTexture in its own GLES context if it so chooses.  This change also
adds the TextureView#setSurfaceTexture method, allowing an app have the
TextureView use a SurfaceTexture that already exists rather than creating a new
one.

Change-Id: Iac9cc917687e4239dd1c24eae553709aa37512da