[llvm] [mlir] [NFC][TableGen] Use `Twine` for Name argument in CodeGenHelpers (PR #163581)

[Rahul Joshi via llvm-commits]

jurahul wrote:

Would like to get this in first before https://github.com/llvm/llvm-project/pull/163820

https://github.com/llvm/llvm-project/pull/163581