## Description
This pull request addresses the issue where the DirectML NuGet pipeline
has error like "##[error]A duplicate file name exists, or the file" in
Windows_CI_GPU_DML_Dev_arm64 step.

### Core Changes

1. **Automation Script**: Introduced bundle_dml_package.ps1 to
orchestrate the merging process:
    - Extracts the base x64 `.nupkg`.
- Merges ARM64 binaries from a supplemental build artifact into the
`runtimes/win-arm64/native` directory.
    - Repackages the resulting structure into a unified `.nupkg`.
2. **Pipeline Integration**: Updated dml-nuget-packaging.yml to include
a final `NuGet_Packaging_DML` stage. This stage is dependent on both the
x64 and ARM64 build stages.
3. **Extended Selection logic**: Updated select_dml_package.ps1 to allow
renaming artifacts (specifically for creating the supplemental ARM64
zip) and more robust package selection for development and release
builds.
4. **Validation Enhancements**: Included updates to
`validate_package.py` and `validate-package.yml` to support
multi-platform verification in future pipeline runs.

---

## Verification Results

The bundling logic was verified through the pipeline logs in the
`NuGet_Packaging_DML` stage.

### Execution Logs
- **Successful Extraction**: The script correctly extracted the
`win-dml-arm64.zip` and the base
`Microsoft.ML.OnnxRuntime.DirectML.1.24.1.nupkg`.
- **Injection Proof**:
- Created the `runtimes/win-arm64/native` directory inside the package
extraction folder.
- Copied `onnxruntime.dll`, `onnxruntime.lib`, and
`onnxruntime_providers_shared.dll` into the ARM64 runtime path.
- **Unified Package Creation**: 7-Zip successfully created the new
archive containing **34 files** (up from 31 in the original x64-only
package).
- **Size Increase**: The package size increased from **~6.6 MB** to
**~12.4 MB**, reflecting the inclusion of binaries for both
architectures.

> [!IMPORTANT]
> **Artifact Note**: When verifying the CI output, the unified
multi-arch package is located in the **`packages`** artifact produced by
the `NuGet_Packaging_DML` stage. Intermediate artifacts like
`drop-nuget-dml` still contain the single-architecture (x64) version.

This cherry-picks the following commits for the release:
- #27350 [Build] Fix python packaging pipeline
- #27349 [Build] Fix DML Nuget Pipeline for Release
- #27334 [DNNL] Fix DNNL build
- #27374 Enable Robust Symlink Support for External Data (HF Cache
Support)

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Co-authored-by: Hariharan Seshadri <shariharan91@gmail.com>