### 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 = tqm
        self._inventory = tqm.get_inventory()
        self._workers = tqm._workers
        self._variable_manager = tqm.get_variable_manager()
        self._loader = tqm.get_loader()
        self._final_q = tqm._final_q
        self._step = context.CLIARGS.get('step', False)
        self._diff = context.CLIARGS.get('diff', False)
        
        
        
        self._queued_task_cache = {}
        
        self._display = display
        
        self._pending_results = 0
        self._pending_handler_results = 0
        self._cur_worker = 0
        
        
        self._blocked_hosts = dict()