[DAGCombine] Transform `shl X, cttz(Y)` to `mul (Y & -Y), X` if cttz is unsupported (#85066)

This patch fold `shl X, cttz(Y)` to `mul (Y & -Y), X` if cttz is
unsupported by the target.
Alive2: https://alive2.llvm.org/ce/z/AtLN5Y
Fixes https://github.com/llvm/llvm-project/issues/84763.