### 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.
else:
                skipped = True
                skip_reason += ", continuing execution for %s" % target_host.name
                
                msg = "end_host conditional evaluated to false, continuing execution for %s" % target_host.name
        elif meta_action == 'role_complete':
            
            
            if task.implicit:
                if target_host.name in task._role._had_task_run:
                    task._role._completed[target_host.name] = True
                    msg = 'role_complete for %s' % target_host.name
        elif meta_action == 'reset_connection':
            all_vars = self._variable_manager.get_vars(play=iterator._play, host=target_host, task=task,
                                                       _hosts=self._hosts_cache, _hosts_all=self._hosts_cache_all)
            templar = Templar(loader=self._loader, variables=all_vars)
            
            
            
            play_context = play_context.set_task_and_variable_override(task=task, variables=all_vars, templar=templar)
            
            
            play_context.post_validate(templar=templar)
            
            
            if not play_context.remote_addr:
                play_context.remote_addr = target_host.address
            
            
            play_context.update_vars(all_vars)