Implement easier way to create and show a simple Overlay/MessageBox

[Al12rs]

Problem

We currently don't have an easy way to create and show a flexible MessageBox from code.

We have an Overlay based MessageBox, system that requires the creation of a new subclass with View and VM for any button combination that isn't "OK Cancel".

We should be able to quickly create a new message box and show it on the fly, without having to create a new UI or VM for it.
The messagebox should be themed of course.

Qt has a pretty good API for messageboxes that allows adding buttons, setting the primary one etc, we want something along those lines.

Options:

Avalonia doesn't offer a native MessageBox component, but it does suggest some third party alternatives in its documentation:
https://docs.avaloniaui.net/docs/basics/user-interface/messagebox

Looking at them, it seems that MessageBox.Avalonia is using DialogHost.Avalonia.

The API offered seem pretty good. A question remains whether these libraries will work well with our particular Multi-Window setup, and whether relaying on them would be preferrable to investing time to develop our own custom solution.