Show tracks from more than one artists in Zune Shell.

[amaid]

// TODO

This is currently blocked because we are currently missing:

• Ability to share AppSettings with the shells, which is needed to build MergedCoreConfig object.
• Ability to perform playback operation on a custom MergedTrackCollection, the plugins provided by the app don't get applied automatically.

Overview

Closes #0

Checklist

This PR meets the following requirements:

• Tested and contains NO breaking changes or known regressions.
• Tested with the upstream branch merged in.
• Tests have been added for bug fixes / features (or this option is not applicable)
• All new code has been documented (or this option is not applicable)
• Headers have been added to all new source files (or this option is not applicable)

Additional info

Not provided

[amaid]

Updated the description with the blockers

@Arlodotexe

[Arlodotexe]

Previously blocked by

1. Ability to share AppSettings with the shells, which is needed to build MergedCoreConfig object.
2. Ability to perform playback operation on a custom MergedTrackCollection, the plugins provided by the app don't get applied automatically.

1. Is unblocked. You can access this via the dataroot passed into your shell - IStrixDataRoot.MergeConfig.
2. Partially unblocked by [improvement] View models implement IDelegatable #245. This will allow us to access the StrixDataRootPluginWrapper, but we forgot to expose the constructor-provided plugins as a property.

Let's finish 2 separately in #280, so it shows in the changelog properly.