BufferItemConsumer: Make creation calls flag-agnostic

It's really annoying to work with these right now since clients have to
juggle two flag-guarded constructors. Instead, add a static create
function that returns a BIC and a Surface.

Also removes flag guards around ConsumerBase::setConsumerIsProtected,
which was never necessary and makes it possible to migrate clients away
from this flag in their code.

BYPASS_IGBP_IGBC_API_REASON=warren buffers

Bug: 398822412
Flag: EXEMPT refactor
Test: compiles, presubmit
Change-Id: I045a8ba804928623fcf7c430be245fd6f2e70bb1