[HLSL] Investigate, update and document the correct function attributes for DXIL ops

[inbelic]

When implementing #117072, it was noted that there are some existing DXIL ops defined in DXIL.td where the currently set DXILAttributes might be less restrictive then they could be, or, do not have any specified attributes. For example, see here and here.

This issue would then track the work of investigating and documenting the correct attributes for DXIL ops, and, then specifying this for existing DXIL ops in DXIL.td

[damyanp]

We're unable to convince ourselves that there's anything to do here.