### 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.
for handler_block in reversed(handler_blocks):
                for handler_task in handler_block.block:
                    if handler_task.name:
                        if not handler_task.cached_name:
                            if handler_templar.is_template(handler_task.name):
                                handler_templar.available_variables = self._variable_manager.get_vars(play=iterator._play,
                                                                                                      task=handler_task,
                                                                                                      _hosts=self._hosts_cache,
                                                                                                      _hosts_all=self._hosts_cache_all)
                                handler_task.name = handler_templar.template(handler_task.name)
                            handler_task.cached_name = True
                        try:
                            
                            
                            
                            
                            candidates = (
                                handler_task.name,
                                handler_task.get_name(include_role_fqcn=False),
                                handler_task.get_name(include_role_fqcn=True),
                            )
                            if handler_name in candidates:
                                return handler_task
                        except (UndefinedError, AnsibleUndefinedVariable):