[AArch64][GlobalISel] Run overlapping_and after legalization

When we have code with truncates, those truncates may be changed into G_ANDs
with constants. These may, in turn, feed into other G_AND instructions.

Running this combine post-legalize allows us to optimize examples like this one:

https://godbolt.org/z/zrGY4dfEW

SDAG currently optimizes the example above so that there is only one `and`.
GISel doesn't optimize it, because the G_AND we'd optimize here is translated
as a G_TRUNC. Later, that G_TRUNC is turned into a G_AND during legalization.

Differential Revision: https://reviews.llvm.org/D110667