[SYCL][UR][Graph] Move L0 simultaneous graph synchronization from SYCL-RT to L0 adapter

[EwanC]

In the graph_impl.cpp SYCL-RT code we currently have a special case for the Level Zero backend that blocks on previous executions of a graph - https://github.com/intel/llvm/blob/sycl/sycl/source/detail/graph_impl.cpp#L1005

This code is backend specific so should be moved into the Unified Runtime Level-Zero v1 adapter in order to be conformance with the UR spec wording from #17658. Defining that a UR command-buffer should be able to be submitted while a previous submission is still executing.

Note that the Level-Zero v2 adapter will implemented this behavior in #17709.