BQ: Get rid of setBufferCount

- Remove setBufferCount from BufferQueueProducer and
  IGraphicsBufferQueueProducer.
- Get rid of the unit tests for it.
- In Surface, convert setBufferCount calls into calls to
  setMaxDequeuedBufferCount.
- Change mOverrideMaxBufferCount to a boolean since it can now be
  derived from mMaxAcquiredBufferCount, mMaxDequeuedBufferCount, and
  mAsyncMode.

Bug 13174928

Change-Id: Ia0adc737fae9e13f186df832b8428a0829041bf9