Fix release workflow WinGet payload handling

[Marc-André Moreau (mamoreau-devolutions)]

Summary

• fix the WinGet bundle fetch script so it no longer depends on a deleted upstream reference directory
• skip Azure signing steps during release dry runs so branch validation runs can complete without production signing secrets
• cache the generated WinGet payload directories in the release workflow to avoid re-downloading them on subsequent runs

Validation

• investigated failing workflow run 22915409281 and confirmed the root cause was the Fetch WinGet CLI bundle step
• dry run succeeded on fix-release after the workflow fixes: 22917258794
• second dry run on the same commit confirmed WinGet cache hits for x64 and arm64: 22917841458