Reevaluate extra support for deferred Memory Allocation

[reble]

We considered the following explicit graph building interfaces for adding a memory allocation owned by the graph:

1. Allocation function returning a reference to the raw pointer, i.e. void*&, which will be instantiated on graph finalization with the location of the allocated USM memory.

2. Allocation function returning a handle to the allocation. Applications use the handle in node command-group functions to access memory when allocated.

3. Allocation function returning a pointer to a virtual allocation, only backed with an actual allocation when graph is finalized or submitted.

[EwanC]

Closing this as we now have a design for graph owned allocations in intel#18001