[llvm] Replace llvm::Any with std::any

llvm::Any had several bugs in the past, due to being sensitive to symbol
visibility. (See D101972 and D108943)

Even with these fixes applied, I still encounter the same issue on
Windows.

Similar to llvm::Optional going away in favor of std::optional, we can
use std::any from C++17.

Using std::any fixes the problem and puts the burden to do it correctly
on the standard library.

Differential Revision: https://reviews.llvm.org/D139532