[llvm] [mlir] mlir/Presburger/MPInt: move into llvm/ADT (PR #94953)

[Arjun P via llvm-commits]

Superty wrote:

If DynamicAPInt is a friend, I believe you can reach inside and set that location to zero (even if the APInt object hasn't been constructed).

https://github.com/llvm/llvm-project/pull/94953