Remove Hard-Coded Font Properties

[robloo]

WinUI hard-coded font-related properties like FontSize for almost every control template. FluentAvalonia copied this over (perhaps from Avalonia's Fluent v1 theme at the time). However, upstream Avalonia has removed these properties and allows them to be inherited everywhere. This is better as it allows setting FontSize on a Window and have it apply to every control in the view.

The discussion is should FluentAvalonia follow upstream Avalonia and remove these hard-coded properties in the control themes? This would deviate from upstream WinUI.