iris: Report use of any in-flight buffers on first draw call after sync boundary.

iris: Report use of any in-flight buffers on first draw call after sync boundary.

This is the main performance trade-off of this cache tracking
mechanism: In order for the seqno vector of buffer objects to be
accurate, they need to be marked as used again every time the batch is
split into a new synchronization section if they remain bound to the
pipeline.  This can be achieved easily by re-using
iris_restore_render_saved_bos() and iris_restore_compute_saved_bos(),
which currently serve a similar purpose across batch buffer
boundaries.

The impact on Piglit drawoverhead results seems to be within a
standard deviation of the current results.

XXX - It might be possible to completely remove the current
      iris_batch::contains_draw flag at a small additional performance
      cost.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3875>