### 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.
'''
        Create a copy of this object and return it.
        '''
        try:
            new_me = self.__class__()
        except RuntimeError as e:
            raise AnsibleError("Exceeded maximum object depth. This may have been caused by excessive role recursion", orig_exc=e)
        for name in self._valid_attrs.keys():
            if name in self._alias_attrs:
                continue
            new_me._attributes[name] = shallowcopy(self._attributes[name])
            new_me._attr_defaults[name] = shallowcopy(self._attr_defaults[name])
        new_me._loader = self._loader
        new_me._variable_manager = self._variable_manager
        new_me._validated = self._validated
        new_me._finalized = self._finalized
        new_me._uuid = self._uuid
        
        if hasattr(self, '_ds'):
            new_me._ds = self._ds
        return new_me
    def get_validated_value(self, name, attribute, value, templar):