[clang] [lldb] [llvm] [mlir] [APInt] Fix APInt constructions where value does not fit bitwidth (NFCI) (PR #80309)

[Nikita Popov via cfe-commits]

nikic wrote:

I think this is ready for review now. I've landed many parts of this PR separately already, and am happy to land this in parts (or split as needed).

https://github.com/llvm/llvm-project/pull/80309