texture_cache: don't count deleted images still waiting to be destroyed

The collector deletes images into a ring that destroys them TICKS_TO_DESTROY
frames later, and until then the driver still counts their memory. Reading the
driver's usage every frame, the collector saw no drop after deleting and kept
deleting 40+ images a frame in aggressive mode long after it had freed enough:
once a session reached the critical threshold, frames took over 100 ms for
seconds at a time.

Keep the bytes deleted into each slot of the ring and leave them out of the
reported usage until the ring destroys them.

0 files changed, 0 insertions, 0 deletions