### 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.
self._tqm.clear_failed_hosts()
                    iterator._host_states[host.name] = prev_host_state
                    for method, what in status_to_stats_map:
                        if getattr(result, method)():
                            self._tqm._stats.decrement(what, host.name)
                    self._tqm._stats.decrement('ok', host.name)
                    
                    self._queue_task(host, task, task_vars, play_context)
                    _processed_results.extend(debug_closure(func)(self, iterator, one_pass))
                    break
                elif next_action.result == NextAction.CONTINUE:
                    _processed_results.append(result)
                    break
                elif next_action.result == NextAction.EXIT:
                    
                    sys.exit(99)
            else:
                _processed_results.append(result)
        return _processed_results
    return inner
class StrategyBase:
    '''
    This is the base class for strategy plugins, which contains some common
    code useful to all strategies like running handlers, cleanup actions, etc.
    '''
    
    
    
    ALLOW_BASE_THROTTLING = True
    def __init__(self, tqm):