[llvm] [ConstantRange] Fix off by 1 bugs in UIToFP and SIToFP handling. (PR #86041)

[via llvm-commits]

AtariDreams wrote:

/cherry-pick https://github.com/llvm/llvm-project/commit/6295e677220bb6ec1fa8abe2f4a94b513b91b786 https://github.com/llvm/llvm-project/commit/12836467b76c56872b4c22a6fd44bcda696ea720 release/18.x

https://github.com/llvm/llvm-project/pull/86041