Investigate source generators for Avalonia styles

[erri120]

We currently don't have any tooling for Avalonia style names. The compiler and the extension we use don't provide any details when styles we want to apply don't exist. Our code (mainly #600) also contains raw hardcoded strings for certain class names that get added/removed dynamically. These names should ideally be auto-generated by some source generator.

If we don't have any tooling around styles and class names, we might run into a situation where we accidentally delete or rename some styles and now parts of our UI looks different because the selector no longer matches.