[llvm] [NFC] Add a new Intrinsics.cpp file for intrinsic code (PR #110078)

[Nikita Popov via llvm-commits]

https://github.com/nikic commented:

What's the motivation for splitting this into a separate file? Is this just so the name matches the name of the header?

https://github.com/llvm/llvm-project/pull/110078