[llvm] [NFC] Reduce copies created of ConstantRange when getting ConstantRangeAttributes. (PR #90335)

[Nikita Popov via llvm-commits]

nikic wrote:

@andjo403 I think the C API would have to do the same as other places that take an APInt, e.g.:
```
LLVMValueRef LLVMConstIntOfArbitraryPrecision(LLVMTypeRef IntTy,
                                              unsigned NumWords,
                                              const uint64_t Words[]);
```
In this case we'd accept the words for both lower and upper.

I'm not sure whether we have any C APIs that return APInt values.

https://github.com/llvm/llvm-project/pull/90335