Use PackageId as AssemblyName

[Arlodotexe]

This PR updates our tooling to use the PackageId as the AssemblyName for components.

It required changes in both Tooling and any components with a custom PackageId due to the single-import. Hopefully this will get cleaner when we have nested components (https://github.com/CommunityToolkit/Tooling-Windows-Submodule/issues/187).

Note that any components using a custom PackageId will need to be updated to define their PackageId before importing ToolkitComponent.SourceProject.props, which requires importing the PackageIdVariant prop from MultiTarget\WinUI.TargetVersion.props first.