additionally, the CreateHelpContent method is now no longer locked to returning an Avalonia `Control`.
the WithHelpContent method also has logic to handle it returning a string directly, and will wrap it in a textblock with h1 style and size 20 font. otherwise it's up to the ContentPresenter for the help content to choose how to display it if it's none of the above mentioned types.
the context can now override a virtual method named `CreateHelpContent` which the setup wizard system will automatically try to use when you use the generic overload taking a generic context type. If the return is null, it skips setting entirely (the default impl is null)
additionally made the discord join link a button with code copied from the about window, and made it centered at the bottom.
- Remove polymorphic base, this only existed because TKMM has a desktop/switch setup prodecure difference and has 2 implementations of the setup wizard. We only need one.
- Remove Systems/UI file split, they're all in Ryujinx.Ava.UI now
- made NotificationHelper instance-based to allow you to encapsulate notifications to a window that magically disappear when the window is closed, instead of switching to showing on the main window.
renamed view models to contexts (like TKMM), however the contexts here are actually of a unique base type; containing aforementioned setup step logic. if the return value is of an error state result, it will prompt a retry of the page.
