### 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 block in new_blocks:
                        iterator._play.handlers.append(block)
                        for task in block.block:
                            task_name = task.get_name()
                            display.debug("adding task '%s' included in handler '%s'" % (task_name, handler_name))
                            task.notified_hosts = included_file._hosts[:]
                            result = self._do_handler_run(
                                handler=task,
                                handler_name=task_name,
                                iterator=iterator,
                                play_context=play_context,
                                notified_hosts=included_file._hosts[:],
                            )
                            if not result:
                                break
                except AnsibleError as e:
                    for host in included_file._hosts:
                        iterator.mark_host_failed(host)
                        self._tqm._failed_hosts[host.name] = True
                    display.warning(to_text(e))
                    continue
        
        handler.notified_hosts = [
            h for h in handler.notified_hosts
            if h not in notified_hosts]
        display.debug("done running handlers, result is: %s" % result)
        return result
    def _filter_notified_failed_hosts(self, iterator, notified_hosts):