[ConstantRangeTest] Add exhaustive intersectWith() test

[ConstantRangeTest] Add exhaustive intersectWith() test

Add a test that checks the intersectWith() implementation against
all 4-bit range pairs. The test uses a more explicit way of
calculating the possible intersections, and checks that the right
one is picked out according to the smallest set heuristic.

This is in preparation for introducing intersectWith() variants that
use different heuristics to pick an intersection range, if there are
multiple possibilities.

llvm-svn: 357119