values_list enhancement - return related value as list, not as different list item

Is your feature request related to a problem? Please describe.
Let's consider following models and query

class User(Model):
    id = fields.IntField(pk=True)
    login = fields.CharField(max_length=32, null=False, unique=True)
    roles = fields.ManyToManyField('models.Role', related_name="users", through="user_role")

class Role(Model):
    id = fields.IntField(pk=True)
    name = fields.CharField(max_length=64, null=False, unique=True)

Query:
users = await User.values_list("login", "roles__name")

It will return the list of {login, role__name}

[
    {
      "roles__name": "admin",
      "login": "admin"
    },
    {
      "roles__name": "string",
      "login": "admin"
    }
]

But the better option here is to return the list-in-list instead

[
    {
      "roles__name": ["admin", "string"],
      "login": "admin"
    }
]

Describe the solution you'd like
I would like to have here an flag to get values grouped, or just make it from default

[
    {
      "roles__name": ["admin", "string"],
      "login": "admin"
    }
]

Describe alternatives you've considered
Obviously it's possible to group it in code, just iterate on list, check if already in list, and append, but i would like to have it on tortoise base code instead

Start at the Python ORM's values_list implementation and its relation traversal for roles__name. Review how many-to-many results are assembled, then add focused coverage for grouped related values and clarify whether grouping is opt-in or the default. Done means the query returns one record per user with related role names collected in a list.