### 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.
hostname = host.get_name()
                    self._variable_manager.clear_facts(hostname)
                msg = "facts cleared"
            else:
                skipped = True
                skip_reason += ', not clearing facts and fact cache for %s' % target_host.name
        elif meta_action == 'clear_host_errors':
            if _evaluate_conditional(target_host):
                for host in self._inventory.get_hosts(iterator._play.hosts):
                    self._tqm._failed_hosts.pop(host.name, False)
                    self._tqm._unreachable_hosts.pop(host.name, False)
                    iterator._host_states[host.name].fail_state = iterator.FAILED_NONE
                msg = "cleared host errors"
            else:
                skipped = True
                skip_reason += ', not clearing host error state for %s' % target_host.name
        elif meta_action == 'end_play':
            if _evaluate_conditional(target_host):
                for host in self._inventory.get_hosts(iterator._play.hosts):
                    if host.name not in self._tqm._unreachable_hosts:
                        iterator._host_states[host.name].run_state = iterator.ITERATING_COMPLETE
                msg = "ending play"
            else:
                skipped = True
                skip_reason += ', continuing play'
        elif meta_action == 'end_host':
            if _evaluate_conditional(target_host):
                iterator._host_states[target_host.name].run_state = iterator.ITERATING_COMPLETE
                iterator._play._removed_hosts.append(target_host.name)
                msg = "ending play for %s" % target_host.name