GraphicBuffer: add optional DetachedBufferHandle

Stores a BufferHub handle that can be used to reattach this
GraphicBuffer back into a BufferHub producer/consumer set. In terms of
GraphicBuffer's relationship with BufferHub, there are three different
modes:

1. Legacy mode: GraphicBuffer is not backed by BufferHub and
   mDetachedBufferHandle must be invalid.
2. Detached mode: GraphicBuffer is backed BufferHub, but not part of a
   producer/consumer set. In this mode, mDetachedBufferHandle must be valid.
3. Attached mode: GraphicBuffer is backed BufferHub and it's part of a
   producer/consumer set. In this mode, mDetachedBufferHandle must be
   invalid.

Note that the DetachedBufferHandle is used as a opaque handle for
GraphicBuffer and it's not exposed to VNDK.

Bug: 38137191
Bug: 69982239
Bug: 70046255
Bug: 70912269
Test: GraphicBuffer_test
Change-Id: I4c3a967cb498291aa175312fdadc84edd3b1a8be