[clang] [llvm] [clang-sycl-linker] Add per-translation-unit device code split mode (PR #196435)

[Yury Plyakhin via cfe-commits]

YuriPlyakhin wrote:

> nit:
> 
> ```c++
> return createStringError(inconvertibleErrorCode(), "error message");
> ```
> 
> can be shortened to
> 
> ```c++
> return createStringError("error message");
> ```

I see this in several places, none of which is touched by this PR, I'll address this as an [NFC] refactoring in a new PR to not pollute this one.

https://github.com/llvm/llvm-project/pull/196435