[autofit] Avoid excessive stem length rounding (#25392). * src/autofit/aflatin.c (af_latin_compute_stem_width): Add argument to pass difference between hinted and unhinted position of base point; use this to adjust the stem width depending on the PPEM so that it doesn't become too large under certain circumstances. Update all callers using value 0 for this argument except... (af_latin_align_linked_edge): Pass position delta of base point to `af_latin_compute_stem_width'.