[HLSL] For RWBuffer adjust the concept expr to support bools

RWBuffer fails compilation since the concept rejects the bool element type. The fix is to update the concept

Repro: https://godbolt.org/z/hExTe3nz1

Start by reproducing the RWBuffer compilation failure with the linked Godbolt example, then trace the HLSL RWBuffer concept expression that rejects the bool element type. Done means the concept accepts bool elements and the reproduction compiles successfully, with relevant compiler tests passing if you locate them.

Written by the indexing model from the issue text.