[FEA] New storage class concept

Part of #110 (Refactor of open address data structures)

Development branch: NVIDIA/cuCollections/refactor

Synopsis

A conceptual list of <key,payload> elements that need not necessarily be contiguous in memory. For example, vector< pair<key,value> > or vector<key> and vector<value> (i.e., AoS vs SoA) could be valid implementations of storage.

TODOs

• Implement classes cuco::storage::array_of_structs and cuco::storage::struct_of_arrays and (optionally) cuco::storage::array_of_structs_of_arrays (closes #103)
• Own the mechanism of atomically updating a given slot using cuda::atomic_ref (closes #183)
• It should provide some mechanism for loading an immutable "window" of slots. The intention is to provide a standard way of using vector load/store operations
• Enable querying if concurrent insert/find operations are possible No longer desired due to operator mixins

References

• https://godbolt.org/z/9bosKoW4v (distinct "ProbingScheme" and "Storage" concepts)

Start with the refactor development branch and read the issue's Godbolt reference for the distinct ProbingScheme and Storage concepts. Define the scope of cuco::storage::array_of_structs and struct_of_arrays, and optionally array_of_structs_of_arrays, then verify that the resulting abstractions support the listed slot-update and immutable-window requirements.