add constraint on args when calling with any as function type

add constraint on args when calling with any as function type

Summary:
When typechecking a call, if the function type is unknown (any or dynamic and the like), then its arguments should coerce to the corresponding type.
This has impact:
- in global inference:
```
class A {
  public $foo;
  public function f($x): void {
    $this->foo->bar($x);
  }
}
```
In the above, $x would have type #1, and we want to record that `#1 <: Tany` to avoid infering mixed
- But also in the general case: see the added test and the inline comments

For now, this is gated by the infer_missing flag. The question is: should it be?

Reviewed By: manzyuk

Differential Revision: D16892210

fbshipit-source-id: 83e93f1a691dbe3338cdd1bfb2c7714228f4f2da