Fix inference with UninhabitedType (#16994)
At the moment, inference fails if an empty dict is used (without
annotation) as one of the types. It's because the constraint solver
can't resolve `dict[str, int]` and `dict[Never, Never]`. However in this
case it's more reasonable to interpret the empty dict as `dict[Any,
Any]` and just using the first type instead. That matches the behavior
of pyright.
```py
T = TypeVar("T")
class A(Generic[T]): ...
def func1(a: A[T], b: T) -> T: ...
def a1(a: A[Dict[str, int]]) -> None:
reveal_type(func1(a, {}))
```
```
# before
main: error: Cannot infer type argument 1 of "func1" (diff)
main: note: Revealed type is "Any" (diff)
# after
main: note: Revealed type is "builtins.dict[builtins.str, builtins.int]"
```
