[ty] Add vararg call benchmarks (#24747)
## Summary
This PR adds some benchmarks for functions that accept varargs and are
called with a large number of arguments, as in:
```python
def accepts_anything(first: int, *args: Any, **kwargs: Any) -> None: ...
accepts_anything(0, ("field_0", 0), ..., ("field_1023", 1023))
```
(Along with a second benchmark in which `*args` is typed as non-`Any`.)
