aco: Transform uniform bitwise instructions to 32-bit if possible.

aco: Transform uniform bitwise instructions to 32-bit if possible.

This allows removing superfluous s_cselect instructions
that come from turning booleans into 64-bit vector condition.

v2 by Daniel Schürmann:
- Make the code massively simpler
v3 by Timur Kristóf:
- Fix regressions, make it work in wave32 mode
- Eliminate extra moves by not always using the SCC definition
- Use s_absdiff_i32 for uniform XOR
- Skip the transformation for uncommon or invalid instructions

Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3450>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3450>