Remove empty list fields from the manifest

[mdanish-kh]

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• Are you working against an Issue?
  • I saw this in PR https://github.com/microsoft/winget-pkgs/pull/194929/files (See Tags: [] field in defaultLocale manifest)

This PR makes it so that empty list fields like Tags: [], Agreements: [] are removed from the manifest before it's serialized.

Validation

Updated unit tests to cover empty lists. For a manual example try:

wingetcreate update VeyonSolutions.Veyon --urls https://github.com/veyon/veyon/releases/download/v4.9.1/veyon-4.9.1.0-win32-setup.exe https://github.com/veyon/veyon/releases/download/v4.9.1/veyon-4.9.1.0-win64-setup.exe --version 2.0.0

and see that Tags: [] is not present in the manifest with this change

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Microsoft Reviewers: Open in CodeFlow