[ValueTracking] Add KnownBits patterns `xor(x, x - 1)` and `and(x, -x)` for...

[ValueTracking] Add KnownBits patterns `xor(x, x - 1)` and `and(x, -x)` for knowing upper bits to be zero

These two BMI pattern will clear the upper bits of result past the
first set bit. So if we know a single bit in `x` is set, we know that
`results[bitwidth - 1, log2(x) + 1] = 0`.

Alive2:
blsmsk: https://alive2.llvm.org/ce/z/a397BS
blsi: https://alive2.llvm.org/ce/z/tsbQhC

Differential Revision: https://reviews.llvm.org/D142271