Adding SurfaceEncoder for encoding FilterFrames

Adding SurfaceEncoder which can be used to encode
custom frame data. In a sense, it is reverse
of what SurfaceTexture does.

SurfaceEncoder takes in frames from a native window and
passes them to an encoder, thus acting like a MediaSource.
It uses GRAlloc buffers underneath for passing data.
The client side sets the geometry, format in the beginning,
which cannot be changed while the recording is going on.

Currently, there is no common pixel format that both
GRAlloc and HAL understand.
Also, the encoder cannot encode using the data from the GRAlloc
buffers.

The SurfaceEncoder_test examines mainly the buffer passage
since true encoding cannot be done at this point.
SimpleDummyRecorder 'reads' the frames in the same thread
as the start(), whereas DummyRecorder 'reads' in a separate
thread much like the MPEG4Writer. The test with DummyRecorder
is much closer to the real encoding implementation.

Related to bug id: 4529323

Change-Id: I58ec19a150f8fe4d6195196dc44f55002b46c7c8