glsl: Use hash tables for opt_constant_propagation() kill sets.

glsl: Use hash tables for opt_constant_propagation() kill sets.

Cuts compile/link time of the fragment shader in #91857 by 19%
(16.28 -> 13.05).

I didn't bother with the acp sets because they're smaller, but it
might be worth doing as well.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=91857
Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Thomas Helland <thomashelland90@gmail.com>
Reviewed-by: Timothy Arceri <t_arceri@yahoo.com.au>
Tested-by: Tapani Pälli <tapani.palli@intel.com>