[ConstantRange] Optimize nowrap region test, remove redundant tests; NFC

Enumerate one less constant range in TestNoWrapRegionExhaustive,
which was unnecessary. This allows us to bump the bit count from
3 to 5 while keeping reasonable timing.

Drop four tests for multiply nowrap regions, as these cover subsets
of the exhaustive test. They do use a wider bitwidth, but I don't
think it's worthwhile to have them additionally now.

llvm-svn: 375369