Update CUDA plugin package outputs (#31722)
## Summary
Update the CUDA plugin pipeline to publish release-ready Linux archives
and split NuGet packages by canonical .NET RID.
## Key changes
- Publish Linux `.tar.gz` archives in the `cuda_ep_cuda12_linux_gz` /
`cuda_ep_cuda13_linux_gz` artifacts alongside the existing platform zip
artifact.
- Generate one NuGet package per enabled RID:
- `Microsoft.ML.OnnxRuntime.EP.Cuda12/13.win-x64`
- `Microsoft.ML.OnnxRuntime.EP.Cuda12/13.win-arm64`
- `Microsoft.ML.OnnxRuntime.EP.Cuda12/13.linux-x64`
- `Microsoft.ML.OnnxRuntime.EP.Cuda12/13.linux-arm64`
- Keep a shared `.csproj`; `pack_nuget.py` selects the package ID and
exact native RID contents at pack time.
- Publish all RID-specific package IDs in pipeline metadata and update
the Windows GPU NuGet test to consume the `win-x64` package.
- Update packaging documentation and local examples to use the canonical
RID names.
## Validation
- YAML and project XML parsing passed.
- Ruff check and format check passed for `pack_nuget.py`.
- Editor diagnostics reported no errors in touched files.
- End-to-end dry packing produced four packages, each containing only
its matching runtime directory.
- PowerShell/tar archive construction was tested locally.
Azure pipeline execution was not run locally.
