Improve tqdm result type checking

[andre487]

In the current implementation return value's type of tqdm(foo) is any:

for (const item of tqdm([{x: 1, y: 2}, {x: 3, y: 4}])) {
    // item has type `any` and one doesn't have type checking when use properties of that
   item.x; // passed
   item.y; // passed
   item.foo; // passed
}

After this patch a result type will be correctly inferred from the input type:

for (const item of tqdm([{x: 1, y: 2}, {x: 3, y: 4}])) {
   item.x; // passed
   item.y; // passed
   item.foo; // error
}

[andre487]

It's the correct form of IteratorResult: the first argument of the type points to the type that will be returned when we have values (done: false), the second – to the value when iterator is done (done: true).