[DAGCombiner] Fold (mul (sra X, BW-1), Y) -> (neg (and (sra X, BW-1), Y))

[DAGCombiner] Fold (mul (sra X, BW-1), Y) -> (neg (and (sra X, BW-1), Y))

(sra X, BW-1) is either 0 or -1. So the multiply is a conditional
negate of Y.

This pattern shows up when type legalizing wide multiplies involving
a sign extended value.

Fixes PR57549.

Reviewed By: RKSimon

Differential Revision: https://reviews.llvm.org/D133399