aco: implement some exclusive scans with inclusive scans

aco: implement some exclusive scans with inclusive scans

exclusive scan lowering uses full wave shift, for iadd/ixor it's faster
to do inclusive scans and subtract/xor the thread's source.

Foz-DB Navi21:
Totals from 21 (0.02% of 132657) affected shaders:
Instrs: 10925 -> 10727 (-1.81%)
CodeSize: 58064 -> 56488 (-2.71%)
Latency: 178471 -> 177928 (-0.30%)
InvThroughput: 24374 -> 24145 (-0.94%)

Reviewed-by: Timur Kristóf <timur.kristof@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24555>