[llvm] [Support][Windows] Add utility function for retrieving a DLL-exported function (PR #97905)

[Alexandre Ganea via llvm-commits]

aganea wrote:

I reverted back to casting to a `void *`. I think having a helper function with all the template wizardy has very low value in terms of cognitive load.

https://github.com/llvm/llvm-project/pull/97905