refactor(api): use hashy hash for looking up api method and event names

This avoids generating khash tables at runtime, and is consistent with
how evalfuncs lookup work.

src/nvim/main.c

@@ -121,7 +121,6 @@ void event_init(void)
   resize_events = multiqueue_new_child(main_loop.events);
 
   // early msgpack-rpc initialization
-  msgpack_rpc_init_method_table();
   msgpack_rpc_helpers_init();
   input_init();
   signal_init();