Address several outstanding LinAlg open items

[jenatali]

Addresses outstanding issues:

• Spec language is ambiguous and potentially insufficient for D3D12_LINEAR_ALGEBRA_MATRIX_CONSTRUCTION_SUPPORT #240: MATRIX_CONSTRUCTION_SUPPORT takes a single Shape input + BOOL output.
• [LinAlg] ThreadGroup Scope Matrices don't expose Flexible Dimension support #244: Design for threadgroup-scope queries changed to match wave-scope.
• [LinAlg] Clarification needed in the Vector Matrix type combinations section #245: Clarified where conversions occur in vector-matrix multiplication requirements tables.

Additional issues heard offline but not filed as an issue: Customers like Vulkan's "show me everything" model, so in addition to the "does this work" question at the API, I've added a full table enumeration API and DDI. The driver may choose to just expose the table to the runtime, and the runtime can search it to answer the more granular support queries, or the driver may choose to expose both kinds of queries. This can make sense if the number of natively supported cases is large (e.g. WARP with SSE2 through AVX512 will produce a very large table, but answering support questions is easy).

The DDI is explicitly documented since it's less obvious how closely it'll map exactly to the API.