Add dataclass tests

[cdce8p]

Current problem

from dataclasses import dataclass, field

@dataclass
class Expandable:
    _api: field()
    var = []

Desired solution

Detect invalid or problematic usage in dataclasses.

Some ideas

• Invalid field call. It should be the value of the assignment
• Missing type annotation
• Missing use of field -> default_factory for mutable types. Careful of ClassVars as it might be intended for them.
• Unsupported-version check as dataclasses require Python 3.7

--
It might be best to create a new checker class for it.

Additional context

No response