bqhelper: Remove support for passing GL fences into BQs

These are going away since they're prone to cause deadlocks,
overcomplicate the API, and have been superceded by normal fd-based
fences (that can be derived from GL fences on most platforms).

Bug: 339705065
Flag: EXEMPT refactor
Test: old tests
Change-Id: I53a1aac877975dc7dd1be70533290141031bd091