Refactor "Settings.UI.Library"

[enricogior]

Settings.UI.Library contains view model and model definitions for the Setting UI app.
It also contains other classes used by other modules (see #10146)

We want to refactor this library in multiple libraries and make each library clean and consistent.

[yuyoyuppe]

in VCM branch, ColorPicker has new dependencies. It references Microsoft.PowerToys.Settings.UI.Library, and in 9cdf485, we're using System.Windows.Forms.dll functionality for overlay image picker dialog.

[Jay-o-Way]

Is this still an issue?