[0035] Consider VectorAccumulateToMemory as dual to VectorAccumulateToDescriptor

**Which proposal does this relate to?**
[0035](https://github.com/microsoft/hlsl-specs/blob/main/proposals/0035-linalg-matrix.md)

**Describe the issue or outstanding question.**
All other "ToDescriptor" operations have a "ToMemory" variant. We should decide if VectorAccumulate also needs one.