SurfaceTexture: clean up some tests

This change cleans a few things up in the SurfaceTexture tests:
- Wraps a few long lines.
- Refactors the multithreading portions of SurfaceTextureGLToGLTest into
  a new test fixture called SurfaceTextureGLThreadToGLTest.
- Changes some of the tests that were creating their own EGLSurface to
  use the SurfaceTextureGLToGLTest fixture.
- Reorders the test functions so that they are immediately below to the
  test fixture that they use.

Change-Id: I0491ce3528a7ff2b4f1e83602ba290269c087297