### Summary

`ansible.template.is_template` tries to loop until it determines if the value is indeed a template.  Which means we could loop extremely large strings, that don't even remotely look like templates, before we bail.

However, we could benefit from moving `Templar.is_possibly_template` to the global scope, and testing whether the value after `jinja_env.preprocess` is even possibly a template, before doing more computationally complex validation.

### Issue Type

Feature Idea

### Component Name

lib/ansible/template/__init__.py

### Additional Information

<!--- Paste example playbooks or commands between quotes below -->
```yaml (paste below)

```


### Code of Conduct

- [X] I agree to follow the Ansible Code of Conduct
return self._available_variables
    @available_variables.setter
    def available_variables(self, variables):
        '''
        Sets the list of template variables this Templar instance will use
        to template things, so we don't have to pass them around between
        internal methods. We also clear the template cache here, as the variables
        are being changed.
        '''
        if not isinstance(variables, Mapping):
            raise AnsibleAssertionError("the type of 'variables' should be a Mapping but was a %s" % (type(variables)))
        self._available_variables = variables
        self._cached_result = {}
    def set_available_variables(self, variables):
        display.deprecated(
            'set_available_variables is being deprecated. Use "@available_variables.setter" instead.',
            version='2.13', collection_name='ansible.builtin'
        )
        self.available_variables = variables
    @contextmanager
    def set_temporary_context(self, **kwargs):