[llvm] [offload][SYCL] Add SYCL Module splitting (PR #119713)

[Fraser Cormack via llvm-commits]

https://github.com/frasercrmck commented:

About the file naming - should it be `SplitSYCLModule.cpp`? It implements the `splitSYCLModule` API, and I think it fits better with the similarly named `SplitModule.cpp` in the same directory. Regardless of where the `SYCL`  goes, I think having `Split` before `Module` keeps things somewhat consistent.

https://github.com/llvm/llvm-project/pull/119713