goadbWriter: impose glyph name length limit

[frankrolf]

All glyph names are subject to a length-limit of 63 characters, and require that they be entirely composed of characters from the following set: A–Z, a–z, 0–9, ‘.’ (period; U+002E FULL STOP), and ‘_’ (underscore; U+005F LOW LINE). Some older implementations may impose a length-limit of 31 characters.

see https://github.com/adobe-type-tools/agl-specification?tab=readme-ov-file#6-assigning-glyph-names-in-new-fonts