About: Use Qt.createComponent to create About Page

This MR replaces the AboutPage QML file with a kirigami-addons AboutPage Form Card. Apps that use a pageStack simply push the dynamically-created component, which pulls the AboutData already for us. For Kasts, as it relies on a page URL directly, we can pull the URL of this dynamically created component, and it works fine.

Kasts seems to make use of Kirigami-Addons already, so this should be a good fit and help centralize some of the logic. 😀 However I believe this requires Kirigami-Addons v1.1.0 or higher, as noted in the Plasma System Settings MR from some months ago porting it to use the same dynamic component.

This MR should not result in any visual difference. I have attached a screenshot, feel free to pixel-peep just in case 😀 On the left is this MR, and on the right is Kasts 24.08.0.

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Let me know if I have made any mistakes, missed anything, or if this is undesirable.

Thanks!