[ty] Respect mixed positional and keyword arguments in TypedDict constructor (#24448)
## Summary
This PR ensures that we allow the following by adding a path for mixed
positional and keyword arguments:
```python
from typing import TypedDict
class Base(TypedDict):
name: str
class ChildKwargs(TypedDict):
name: str
count: int
def _(base: Base):
ok_union_mapping = ChildKwargs(base, count=1)
```
Closes https://github.com/astral-sh/ty/issues/3225.