Processes `HLSLResourceBindingAttr` attributes that represent
`register(c#)` annotations on default constant buffer declarations and
applies its value to the buffer layout. Any default buffer declarations
without an explicit `register(c#)` annotation are placed after the
elements with explicit layout.
This PR also adds a test case for a `cbuffer` that does not have
`packoffset` on all declarations. Same layout rules apply here as well.
Fixes#126791
Translates `cbuffer` declaration blocks to `target("dx.CBuffer")` type. Creates global variables in `hlsl_constant` address space for all `cbuffer` constant and adds metadata describing which global constant belongs to which constant buffer. For explicit constant buffer layout information an explicit layout type `target("dx.Layout")` is used. This might change in the future.
The constant globals are temporary and will be removed in upcoming pass that will translate `load` instructions in the `hlsl_constant` address space to constant buffer load intrinsics calls off a CBV handle (#124630, #112992).
See [Constant buffer design
doc](https://github.com/llvm/wg-hlsl/pull/94) for more details.
Fixes#113514, #106596
