[HLSL] Read Only Resources incorrectly allow writing

[V-FEXrt]

Resources like Buffer and StructuredBuffer are supposed to be read only but this is not currently enforced.

Ex: https://hlsl.godbolt.org/z/sqMMffh6K fails under DXC but compiles under clang.

This is a bug that should be fixed.

[llvmbot]

@llvm/issue-subscribers-bug

Author: Ashley Coleman (V-FEXrt)

Resources like `Buffer` and `StructuredBuffer` are supposed to be read only but this is not currently enforced.

Ex: https://hlsl.godbolt.org/z/sqMMffh6K fails under DXC but compiles under clang.

This is a bug that should be fixed.