### 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.
'''
        Loads an included YAML file of tasks, applying the optional set of variables.
        '''
        display.debug("loading included file: %s" % included_file._filename)
        try:
            data = self._loader.load_from_file(included_file._filename)
            if data is None:
                return []
            elif not isinstance(data, list):
                raise AnsibleError("included task files must contain a list of tasks")
            ti_copy = self._copy_included_file(included_file)
            
            
            
            tags = included_file._task.vars.pop('tags', [])
            if isinstance(tags, string_types):
                tags = tags.split(',')
            if len(tags) > 0:
                if len(included_file._task.tags) > 0:
                    raise AnsibleParserError("Include tasks should not specify tags in more than one way (both via args and directly on the task). "
                                             "Mixing tag specify styles is prohibited for whole import hierarchy, not only for single import statement",
                                             obj=included_file._task._ds)
                display.deprecated("You should not specify tags in the include parameters. All tags should be specified using the task-level option",
                                   version='2.12', collection_name='ansible.builtin')
                included_file._task.tags = tags
            block_list = load_list_of_blocks(
                data,