[libsycl] add USM alloc/free functions (#184111)
Depends on https://github.com/llvm/llvm-project/pull/184110
This is part of the SYCL support upstreaming effort. The relevant RFCs
can be found here:
https://discourse.llvm.org/t/rfc-add-full-support-for-the-sycl-programming-model/74080
https://discourse.llvm.org/t/rfc-sycl-runtime-upstreaming/74479
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Signed-off-by: Tikhomirova, Kseniya <kseniya.tikhomirova@intel.com>
