nir/scheduler: Add an option to specify what stages share memory for I/O

nir/scheduler: Add an option to specify what stages share memory for I/O

The scheduler has code to handle hardware that shares the same memory
for inputs and outputs. Seeing as the specific stages that need this is
probably hardware-dependent, this patch makes it a configurable option
instead of hard-coding it to everything but fragment shaders.

Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5561>