### 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
            return None
        cur_pass = 0
        while True:
            try:
                self._results_lock.acquire()
                if do_handlers:
                    task_result = self._handler_results.popleft()
                else:
                    task_result = self._results.popleft()
            except IndexError:
                break
            finally:
                self._results_lock.release()
            original_host = task_result._host
            original_task = task_result._task
            
            role_ran = False
            if task_result.is_failed():
                role_ran = True
                ignore_errors = original_task.ignore_errors
                if not ignore_errors:
                    display.debug("marking %s as failed" % original_host.name)
                    if original_task.run_once:
                        
                        for h in self._inventory.get_hosts(iterator._play.hosts):
                            if h.name not in self._tqm._unreachable_hosts: