[pfr] Robustify bitmap strike handling (#47514). We did a binary search for a charcode without ensuring that the searched data is ordered. Validating the order is now done lazily, this is, the first access to a bitmap glyph triggers the order check in the corresponding bitmap strike. * src/pfr/pfrtypes.h (PFR_BitmapFlags): New values `PFR_BITMAP_VALID_CHARCODES' and `PFR_BITMAP_CHARCODES_VALIDATED'. * src/pfr/pfrsbit.c (pfr_lookup_bitmap_data): Make `flags' argument a pointer. Handle new PFR_BITMAP_XXX flags. (pfr_slot_load_bitmap): Updated.