[♻️ Housekepping] Until .NET 9 we should avoid Application.MainPage

[pictos]

The .NET MAUI team is deprecating the usage of Application.MainPage because it, normally, isn't what devs/we expect to be. In a MultiWindow scenario it can return the wrong Page.

One way to workaround this is to change Application.Current.MainPage to Application.Current.Windows[0].Page.

At least for me, isn't 100% clear what Windows[0] means:

• it's the first window at collection
• it's the topmost window
• it's the focused window

For join the discussion at .NET MAUI repo, please go here.

Maybe, today we already have a bug for multi-window apps, but since no user has reported any issue we don't need to rush on this.