### Summary

Executing a playbook with many hosts, there is massive overhead in checking whether the hosts list is a pattern, see for yourself on this callgrind graph:

![grafik](https://user-images.githubusercontent.com/3154871/111359016-4a4bf480-868b-11eb-8c8f-55b6a6a10bd7.png)

https://github.com/ansible/ansible/blob/da60525610a384bb04833b1c6429d9db6a87ef64/lib/ansible/vars/manager.py#L490

That check has quadratic runtime with the number of hosts - with a lot of hosts, commenting that check out reduces runtime manyfold.

### Issue Type

Bug Report

### Component Name

variable manager

### Ansible Version

2.10.5, devel

### OS / Environment

Ubuntu

### Steps to Reproduce

```yaml
- hosts: localhost
  tasks:
    - set_fact:
        extra_tasks: true # compute it
        hosts: "{{ [an, array, with, 5100, computed, hosts] }}"

- hosts: "{{ hostvars.localhost.hosts }}"
  vars:
    extra_tasks: "{{ hostvars.localhost.do_extra_tasks }}"
  tasks:
   # some more tasks here
    - name: Execute extra tasks
      command: /bin/true # example
      when: extra_tasks
```

### Expected Results

Execute in tens of seconds.

### Actual Results

Take over 5 minutes to execute.
"""Continue to next result"""
        self.next_action.result = NextAction.CONTINUE
        return True
    do_c = do_continue
    def do_redo(self, args):
        """Schedule task for re-execution. The re-execution may not be the next result"""
        self.next_action.result = NextAction.REDO
        return True
    do_r = do_redo
    def do_update_task(self, args):
        """Recreate the task from ``task._ds``, and template with updated ``task_vars``"""
        templar = Templar(None, variables=self.scope['task_vars'])
        task = self.scope['task']
        task = task.load_data(task._ds)
        task.post_validate(templar)
        self.scope['task'] = task
    do_u = do_update_task
    def evaluate(self, args):
        try:
            return eval(args, globals(), self.scope)
        except Exception:
            t, v = sys.exc_info()[:2]
            if isinstance(t, str):
                exc_type_name = t
            else:
                exc_type_name = t.__name__
            display.display('***%s:%s' % (exc_type_name, repr(v)))
            raise
    def do_pprint(self, args):