pan/bi: Track liveness while scheduling

pan/bi: Track liveness while scheduling

If we know that a value is killed in the next tuple, there is no need to
write it out to the register file. We already handled this as a packing
fixup. However, avoiding this write also frees up an extra slot in the
register block, which offers additional scheduling freedom. To take
advantage of this, we extend liveness analysis to work while scheduling,
and modify the schedulable predicate accordingly.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11123>