[JS] Support for AsyncIterator protocol

[Lanayx]

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#the_async_iterator_and_async_iterable_protocols

TS definition

interface IteratorYieldResult<TYield> {
    done?: false;
    value: TYield;
}

interface IteratorReturnResult<TReturn> {
    done: true;
    value: TReturn;
}

type IteratorResult<T, TReturn = any> = IteratorYieldResult<T> | IteratorReturnResult<TReturn>;

interface AsyncIterator<T, TReturn = any, TNext = any> {
    // NOTE: 'next' is defined using a tuple to ensure we report the correct assignability errors in all places.
    next(...[value]: [] | [TNext]): Promise<IteratorResult<T, TReturn>>;
    return?(value?: TReturn | PromiseLike<TReturn>): Promise<IteratorResult<T, TReturn>>;
    throw?(e?: any): Promise<IteratorResult<T, TReturn>>;
}

interface AsyncIterable<T, TReturn = any, TNext = any> {
    [Symbol.asyncIterator](): AsyncIterator<T, TReturn, TNext>;
}

interface AsyncGenerator<T = unknown, TReturn = any, TNext = any> extends AsyncIteratorObject<T, TReturn, TNext> {
    // NOTE: 'next' is defined using a tuple to ensure we report the correct assignability errors in all places.
    next(...[value]: [] | [TNext]): Promise<IteratorResult<T, TReturn>>;
    return(value: TReturn | PromiseLike<TReturn>): Promise<IteratorResult<T, TReturn>>;
    throw(e: any): Promise<IteratorResult<T, TReturn>>;
    [Symbol.asyncIterator](): AsyncGenerator<T, TReturn, TNext>;
}

interface AsyncIterable<T, TReturn = any, TNext = any> {
    [Symbol.asyncIterator](): AsyncIterator<T, TReturn, TNext>;
}
interface AsyncIterableIterator<T, TReturn = any, TNext = any> extends AsyncIterator<T, TReturn, TNext> {
    [Symbol.asyncIterator](): AsyncIterableIterator<T, TReturn, TNext>;
}
interface AsyncIteratorObject<T, TReturn = unknown, TNext = unknown> extends AsyncIterator<T, TReturn, TNext> {
    [Symbol.asyncIterator](): AsyncIteratorObject<T, TReturn, TNext>;
}

TS implementation has 3 type parameters, but because in F# we can't unify 'T and 'TReturn in one type, I've added only 'T version (actually just extending existing type)