[Bitmap fonts] Add support for scaling.

[bruvzg]

Adds import option for the bitmap fonts to enable scaling support (integer or arbitrary).

Fixes #80497
Fixes godotengine/godot-proposals#6150

[akien-mga]

Looks good to me. Needs rebase.

[akien-mga]

Looks good to me. Needs rebase.

Poke :)

[akien-mga]

Thanks!

[sandord]

Great work!

I don't think the default scaling configuration is correct though because my pixel art fonts all became very large. This is due to the default font size that is set in the theme (I think it is 16) and that setting used to be ignored.

[rakkarage]

also seems to push the right side of editor off-screen after enabling? and reload project?
quit - delete .godot/imported (not .godot/editor) - reload fixes it
reload breaks it again...
quit - delete .godot/imported (not .godot/editor) - reload fixes it
reload breaks it again...
etc...

[Calinou]

@sandord I suppose this means there's a small degree of compatibility breakage with this PR, but I think the new default behavior is what 99% of people expect when changing font size on a bitmap font (unless there is special casing that makes it ignore a non-overridden font size – I didn't test). So I'd prefer keeping the default to Enabled (Fractional).¹

On the other hand, this approach is contrary to what this comment suggests. cc @bruvzg

@rakkarage Please open a separate issue with a minimal reproduction project attached.
Edit: Issue opened: #83853

Footnotes

1. Remember that if you use integer scaling in the Viewport itself, you don't need to use Enabled (Integer) if you're careful about the font size setting – it's just a helper to ensure you don't accidentally use fractional font sizes for pixel art fonts. ↩