Make waiting_fd behaviour per-IO. (#13127)

- `rb_thread_fd_close` is deprecated and now a no-op.
- IO operations (including close) no longer take a vm-wide lock.

vm.c

@@ -3230,7 +3230,6 @@ ruby_vm_destruct(rb_vm_t *vm)
     return 0;
 }
 
-size_t rb_vm_memsize_waiting_fds(struct ccan_list_head *waiting_fds); // thread.c
 size_t rb_vm_memsize_workqueue(struct ccan_list_head *workqueue); // vm_trace.c
 
 // Used for VM memsize reporting. Returns the size of the at_exit list by
@@ -3285,7 +3284,6 @@ vm_memsize(const void *ptr)
 
     return (
         sizeof(rb_vm_t) +
-        rb_vm_memsize_waiting_fds(&vm->waiting_fds) +
         rb_st_memsize(vm->loaded_features_index) +
         rb_st_memsize(vm->loading_table) +
         rb_vm_memsize_postponed_job_queue() +