message: Improve coroutine, remove COROG.current_coro.
diff: @@ -78,15 +78,14 @@ int coro_init(void)
  static void resume_php_stack(coro_task *task)
  {
  - COROG.current_coro = task;
  - swTraceLog(SW_TRACE_COROUTINE,"sw_coro_resume coro id %d", COROG.current_coro->cid);
  + swTraceLog(SW_TRACE_COROUTINE,"sw_coro_resume coro id %d", task->cid);
  task->state = SW_CORO_RUNNING;
  - EG(current_execute_data) = task->yield_execute_data;
  /* set vm stack to global */
  task->origin_stack = COROG.origin_vm_stack;
  task->origin_vm_stack_top = COROG.origin_vm_stack_top;
  task->origin_vm_stack_end = COROG.origin_vm_stack_end;
  /* resume vm stack */
  + EG(current_execute_data) = task->yield_execute_data;
  EG(vm_stack) = task->yield_stack;
  EG(vm_stack_top) = task->yield_vm_stack_top;
  EG(vm_stack_end) = task->yield_vm_stack_end;
  @@ -245,7 +244,6 @@ static void sw_coro_func(void *arg)
  {
  swoole_call_hook(SW_GLOBAL_HOOK_ON_CORO_START, task);
  }
  - COROG.current_coro = task;
  swTraceLog(SW_TRACE_COROUTINE, "Create coro id: %d, coro total count: %d, heap size: %zu", cid, COROG.coro_num, zend_memory_usage(0));
  EG(current_execute_data) = task->execute_data;
  @@ -393,7 +391,6 @@ void sw_coro_close()
  EG(vm_stack_end) = task->origin_vm_stack_end;
  efree(task->stack);
  COROG.coro_num--;
  - COROG.current_coro = NULL;
  if (OG(active))
  {
  