Proposal for versioning the NonSemantic.Shader.DebugInfo Instruction Set

The SPIRV working group is currently discussing changes to the [NonSemantic.Shader.Debuginfo.100](https://github.khronos.org/SPIRV-Registry/nonsemantic/NonSemantic.Shader.DebugInfo.100.html) (NSDI.100) instruction set. To support this, we need to introduce a formal versioning system to the NSDI spec. This will affect how the instruction set is imported into SPIR-V modules and will have downstream effects on tooling.

The core idea is to follow the same versioning scheme used by [Clspv Reflection](https://github.khronos.org/SPIRV-Registry/nonsemantic/NonSemantic.ClspvReflection.html).

1. **Versioned imports**: The import instruction will now specify a version, replacing the current hardcoded `100`: `%1 = OpExtInstImport "NonSemantic.Shader.DebugInfo.`.
- For compatibility, we will start versioning at `100`.
- Tools that don't understand new instructions may reject the module outright or try to be flexible at parsing instructions that they may not understand.
3. **Unified spec document**: The specification document itself will be versioned internally.
- **New URL**: The spec will live at a single, version-neutral URL: `.../NonSemantic.Shader.DebugInfo.html`
- **Internal versioning**: The document will be updated to match the ClspvReflection spec:
- A "_Latest version_" and "_Date_" section will be added to the top.
- Changes will be documented inline (e.g., "_...this operand is missing before version N._").

I would like to gather opinions on this proposal. Please share any thoughts, concerns, or requirements we should keep in mind as we formalize these changes.

@baldurk @danginsburg @s-perron @sajjadmirzanv @chaocNV for visibility. If you know of any others who may be affected by this, please tag them as well. Thanks.