Add libgui bq_consumer_attach_callback flag

Add a flag for enabling IProducerListener callback when the consumer
attaches a buffer.

Bug: 353202582
Flag: EXEMPT adding flag
Test: n/a
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:dd7c1cf29e5940d16b8293c5f758f344f021f00f)
Merged-In: Ieaa25ed05d04a33de47de7ee3296e4bf1dde7a26
Change-Id: Ieaa25ed05d04a33de47de7ee3296e4bf1dde7a26