Improvements to 3D text spacing

3D text built through Text3D now gets character spacing from glyph advance data instead of deriving spacing from each character outline's maximum x extent.

In practice this makes 3D text spacing better match 2D text, especially for strings containing whitespace. The change is most noticeable in snappers that build meshes from text outlines, such as 3D Text.

Improvements to 3D text spacing

3D text created through Text3D or meshFromText(...) may get a different final width and character layout than before.

This also affects existing content when older drawings are opened in 17.5.

If code depends on previous text extents, alignment, or placement based on the old spacing behavior, those cases may need to be reviewed.