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

[Shilei Tian via llvm-commits]

shiltian wrote:

> Would you mind if we introduce a `llvm/Transforms/SYCL/` directory and put this functionality in there? We are going to add more SYCL-specific passes anyway.

I don't mind it, but I'd do a RFC.

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