DO NOT MERGE libgui: Remove IGBC::BufferItem

Removes IGraphicBufferConsumer::BufferItem. Depends on the
following changes:
    I187b3a7d05196b6289596afac8fb9a9d4aebff76
    I0ddd38df37500cfd6b21d1e768ed14e39c5cd9fc

Cherry-pick of Id1fa56d092188f2cb712768d5d2fc6a9027fb73c

Change-Id: I3edf0db8fba656fd78e18a5a7f1137f0fb6b237d
15 files changed