[llvm] [libsycl] Initial prefetch implementation for queue (PR #212104)

[Kseniya Tikhomirova via llvm-commits]

KseniyaTikhomirova wrote:

I have the only comment left and after I am going to approve and merge this PR. @sergey-semenov FYI, this PR is USM-related. Feel free to provide pre- or post-commit comments.

https://github.com/llvm/llvm-project/pull/212104