Replace the parallel-arrays (struct-of-arrays) ROM method table
layout with an array-of-structs layout where each mrb_mt_entry
bundles its function pointer and symbol key together.
New MRB_MT_ENTRY() and MRB_MT_ROM_TAB() macros simplify ROM table
definitions from a 3-part pattern (SIZE define + anonymous struct +
mrb_mt_tbl) to a 2-part pattern (entries array + mrb_mt_tbl).
Internal mt_* functions in class.c are simplified: single memmove/
memcpy operations replace paired key+value operations.
Co-authored-by: Claude <noreply@anthropic.com>
Yukihiro "Matz" Matsumoto
bde2202100