dillon1000/react

Merge isObject branches (#21226)

We assume that isArray and getIteratorFn are only called on objects.

So we shouldn't have to check that again and again, and then check a flag.

We can just stay in this branch.

There is a slight semantic breakage here because you could have an
iterator on a function, such as if it's a generator function. But that's
not supported and that currently only works at the root. The inner slots
don't support this.

So this just makes it consistent.