[Bug] Class method 'self' looses special self scope with added type annotation

Nobody has claimed this yet.

Got send here from 'vscode-python' https://github.com/microsoft/vscode-python/issues/11593

* **Editor name and version**: VS Code version: 1.44.2
* **Platform**: Windows_NT x64 10.0.17134
* **Color scheme**: Custom (close to Monokai)
* **MagicPython version**: Dunno which vscode uses

Without type annotation everything is just fine.

When a type annotation is added to the `self` parameter the special scope for `self` is missing.

## Steps to reproduce:

Paste the following code into a *.py file and inspect the `self` parameter with the developer token inspect tool. Like in the screenshots above.
The `self` parameter of the `bad_func` should show the actual scopes and the `self` parameter of the `good_func` should show the expected scopes.
```
class Test:
def bad_func(self: Test):
pass

def good_func(self):
pass
```

Start with the reproduced Python snippet and inspect the token scopes for the annotated and unannotated self parameters using the developer token inspect tool. Trace the syntax-highlighting path that handles class method parameters; done means self: Test retains the same special self scopes as unannotated self.

Written by the indexing model from the issue text.