[InstCombine] Support arbitrary const shift amount for `lshr (sext i1 ...)`

Add lshr (sext i1 X to iN), C --> select (X, -1 >> C, 0) case. This expands
C == N-1 case to arbitrary C.

Fixes PR52078.

Reviewed By: spatel, RKSimon, lebedev.ri

Differential Revision: https://reviews.llvm.org/D111330