nir/algebraic: optimize (a & b) & (a & c) ==> (a & b) & c

shader-db with ACO:
    3 shaders have -0.57% average decrease in the code size

Reviewed-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/32449>

src/compiler/nir/nir_opt_algebraic.py

@@ -223,6 +223,7 @@ optimizations = [
    (('~ffmaz', a, ('fmulz(is_used_once)', b, c), ('fmulz(is_used_once)', b, d)), ('fmulz', b, ('ffmaz', a, c, d))),
    (('iadd', ('imul', a, b), ('imul', a, c)), ('imul', a, ('iadd', b, c))),
    (('iadd', ('ishl', b, a), ('ishl', c, a)), ('ishl', ('iadd', b, c), a)),
+   (('iand', ('iand', a, b), ('iand(is_used_once)', a, c)), ('iand', ('iand', a, b), c)),
    (('iand', ('ior(is_used_once)', a, b), ('ior(is_used_once)', a, c)), ('ior', a, ('iand', b, c))),
    (('ior', ('iand(is_used_once)', a, b), ('iand(is_used_once)', a, c)), ('iand', a, ('ior', b, c))),
    (('ieq', ('iand', a, '#b(is_pos_power_of_two)'), b), ('ine', ('iand', a, b), 0)),