sfnt/otf: support CID-keyed CFF fonts

- Resolve glyph-specific local subroutines through FDSelect and FDArray.
- Track stem hints and skip hint masks while decoding CharStrings.
- Reject unsupported CharString operators instead of silently continuing.
- Propagate detailed results from SFNT header parsing.
- Reject CFF2 fonts as unsupported instead of invalid.
- Stop loader fallback when a format is unsupported.

issue: #4614, #4670

Co-Authored-By: Ralf Preininger (rpreininger)