Improvements to set and binding allocations

As mentioned in #614 there are some potential improvements that could be made to descriptor allocation. Currently descriptors are allocated before attempting to resolve via DirectResourceAccess. The potential sharing could be considered earlier so that descriptors are assigned to DRA.

Start by reading issue #614 and tracing descriptor allocation through DirectResourceAccess. Determine how potential sharing could be considered before descriptors are allocated and how descriptors would then be assigned to DRA; done means the allocation flow reflects that sharing without losing required bindings.

Written by the indexing model from the issue text.