[llvm] [KnownBits] Add KnownBits::makeConstantRange to determine the known bits from a pair of unsigned lo/hi bound values (PR #107080)

[Simon Pilgrim via llvm-commits]

RKSimon wrote:

Are people happy for me to use KnownBits -> ConstantRange -> KnownBits paths ? My WIP patches already do this but I'd convinced myself that I'd immediately get feedback asking me to remove the ConstantRange dependency :( 

https://github.com/llvm/llvm-project/pull/107080