[NFC][DAGCombine][X86][AArch64] Tests for 'A - (A & (B - 1))' pattern (PR44448)

https://rise4fun.com/Alive/ZVdp

Name: ptr - (ptr & (alignment-1))  ->  ptr & (0 - alignment)
  %mask = add i64 %alignment, -1
  %bias = and i64 %ptr, %mask
  %r = sub i64 %ptr, %bias
=>
  %highbitmask = sub i64 0, %alignment
  %r = and i64 %ptr, %highbitmask

The main motivational pattern involes pointer-typed values,
so this transform can't really be done in middle-end.

See
  https://bugs.llvm.org/show_bug.cgi?id=44448
  https://reviews.llvm.org/D71499