Classes with `__slots__` require that their subclasses have the same amount of slots

**Describe the bug**
Subclasses `__slots__` incorrectly require that the tuple be the same length as base classes.

**Code or Screenshots**
```py
# pyright: strict
import asyncio

class SpamProtocol(asyncio.Protocol):
__slots__ = ("ham", "eggs") # Tuple size mismatch, expected 0 but received 2

```

**VS Code extension or command-line**
Command Line Tool 1.1.406 (1.1.405 doesn't appear to have this issue)

No source file or test is named in the report. Reproduce the strict-mode example with a subclass of asyncio.Protocol using two __slots__, then trace the diagnostic that reports a tuple-size mismatch; done means valid subclass slots no longer trigger that error and the regression is covered by a test.

Written by the indexing model from the issue text.