[NFC][InstCombine] Revisit canonicalize-constant-low-bit-mask-and-icmp-s*...

[NFC][InstCombine] Revisit canonicalize-constant-low-bit-mask-and-icmp-s* tests in preparatio for PR42198.

The `icmp sgt`/`icmp sle` variants are, too, miscompiles:
https://rise4fun.com/Alive/JFNP
https://rise4fun.com/Alive/jHvL
A precondition 'x != 0' was forgotten by me.

While ensuring test coverage for `-1`, also add test coverage
for `0` mask. Mask `0` is allowed for all the folds,
mask `-1` is allowed for all the folds with unsigned `icmp` pred.
Constant mask `0` is missed though.

https://bugs.llvm.org/show_bug.cgi?id=42198

llvm-svn: 362910