[llvm] [offload][SYCL] Add SYCL Module splitting. (PR #131347)

[Maksim Sabianin via llvm-commits]

maksimsab wrote:

I could change the main splitting method from `SYCLModuleSplit` to:
```cpp

using FunctionCategorizer = function_ref<std::string(const Function &F)>; // Computes the category for the function.

using PostSplitCallbackType = function_ref<void(std::unique_ptr<Module>); // Accepts the split Module for further handling.

void SplitModuleByCategory(std::unique_ptr<Module> M, FunctionCategorizer FC, PostSplitCallbackType Callback);
```

This function would map functions/kernels according to their computed categories. This interface allows reusing for purposes other than SYCL and it doesn't require using SYCL-specifics.

What do you think about this?

https://github.com/llvm/llvm-project/pull/131347