[llvm] [libsycl] extend sycl::event API with get_wait_list, wait_and_throw and default ctor (PR #205860)

[Kseniya Tikhomirova via llvm-commits]

KseniyaTikhomirova wrote:

Hi @dvrogozh, @sergey-semenov, @bader, @YuriPlyakhin this PR extends implementation of sycl::event class with a few more methods.
Could you please review?

https://github.com/llvm/llvm-project/pull/205860