[clang] [CIR][NFC] Cleanup builtin helper function interfaces (PR #169586)

[Andy Kaylor via cfe-commits]

andykaylor wrote:

At this point `emitIntrinsicCallOp` is a very thin wrapper around `cir::LLVMIntrinsicCallOp::create` but I think it still makes the code slightly cleaner.

https://github.com/llvm/llvm-project/pull/169586