libgui: Add support for unlimited slot BufferQueues

BufferQueues can now be of unlimited size, according to the wishes of
the producer.

We add four new methods:

- IGBC::allowUnlimitedSlots, which permits the IGBP to call
  extendSlotCount
- IGBP::extendSlotCount, which increases the total available slot count
  to a fixed number and notifies the consumer via
  ICL::onSlotCountChanged
- ICL::onSlotCountChanged, which notifies the consumer to resize its
  personal slot vector
- IGBC::getReleasedBuffersExtented, which is like getReleasedBuffers but
  with an arbitrary sized bitvector instead of a fixed 64 bit vector

The internal representation of the slots in BufferQueueCore is now a
vector instead of an array, and can grow (but not shrink). The only
consumers of these new APIs are intented to be Surface and ConsumerBase.
Everything else is being migrated away from IGBP/IGBC anyway.

This is part of go/warren-buffers.

Bug: 341359814
Flag: com.android.graphics.libgui.flags.wb_unlimited_slots
Test: new tests, old tests

Change-Id: I0df872b9d6f9273854cc07a88d29b65451e1832a