Allow BlastBufferQueue to acquire an additional buffer

We want to be able to send buffers from BlastBufferQueue to the server
as soon as possible. This allows us among other things, dropping the
oldest buffer when multiple buffers with timestamps are queued up.
To support this behavior with BlastBufferQueue, we need to acquire an
additional buffer and send it to SurfaceFlinger.

This requires changing the consumer owned by BlastBufferQueue to
acquire an additional buffer. This change is safe because we will only
acquire the buffer if its not droppable, maintaining the contract
with the producer.

If the buffer is not droppable, i.e. the producer is in sync mode, once
the buffer has been queued, the buffer is owned by the queue until it
is released or acquired by the consumer. By acquiring an additional
buffer, we transfer the ownership to the consumer earlier. The server
has more info to make decisions faster. The producer still has access
the same number of buffers and is unaffected.

If the producer is in async mode, then this buffer may be released by
the producer when trying to queue a buffer. So we check if the buffer is
droppable, and we do not acquire the extra buffer in this scenario.

Test: atest BlastBufferQueueTests android.media.cts.PresentationSyncTest
Bug: b/176507654, b/176967609
Change-Id: I494a9edcbea0b1c297ee75df2b840d8328e59eca