[ty] Infer `dict(**TypedDict)` in `TypedDict` context (#24709)
## Summary
Given, e.g., `def f() -> TD: return dict(**src)`, we now infer
`dict(**src)` as matching `TD` if `src` is `TD`, for example. So the
following are accepted, whereas on main they all produce diagnostics:
```python
from typing import TypedDict
class TD(TypedDict):
x: int
y: str
src: TD = {
"x": 1,
"y": "foo",
}
x: TD = dict(**src)
def f() -> TD: return dict(**src)
```
