[llvm] Refactor determinePointerAccessAttrs to a dedicated function to colle… (PR #84869)

[Arthur Eubanks via llvm-commits]

https://github.com/aeubanks commented:

since this actually makes the existing code worse without any new functionality, let's keep this change as part of the main FunctionAttrs PR

also, you should be able to return a `std::tuple` like [here](https://github.com/llvm/llvm-project/blob/536e0ebaaa842471ae91bbda4f8cc1821690861e/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp#L763) and nicely separate it in the caller like [here](https://github.com/llvm/llvm-project/blob/42ecccfe346daf342b6c46a6a471ba5ed99b1139/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp#L809)

https://github.com/llvm/llvm-project/pull/84869