Add interface fonts options

[williamchange]

• Resolves Improved Interface Font #1406

Adds custom font/size options

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If system fonts are enabled, sans-serif will be used be in place of the custom main/medium/bold fonts that are set in preferences.

These settings could probably be applied without restarting, but I am getting a lot of "fd" is null errors if I do that so this is what I have for now.

[Calinou]

If system fonts are enabled, sans-serif will be used be in place of the custom main/medium/bold fonts that are set in preferences.

It might look better to use a tailored set of system font names according to the platform, as per this proposal:

• Use a modern font stack in aliases used for system font loading (serif, sans-serif, …) godotengine/godot-proposals#5767

This can be implemented in scripting by checking for the current OS and using the relevant font name.

[williamchange]

SF Pro wasn't available on my machine so I have to get it from https://developer.apple.com/fonts/ to test on macOS

It seems to have problems with MSDF rendering so I only added Windows changes for now

[williamchange]

Added option to switch between msdf/oversampling

[Calinou]

I think exposing a MSDF toggle makes sense to fix fonts with self-intersecting outlines, but exposing oversampling is kind of a double-edged sword. Setting it too high will make small text look grainy (only zoomed-in graphs will benefit from oversampling).

Fixing rendering of MSDF fonts with self-intersecting outlines requires godotengine/godot#61555. It works, but it adds a lot of binary size for niche functionality, so we'd prefer avoiding it if possible.

[williamchange]

Removed oversampling options