[RFC]: Achieve feature parity with async.js

### Description

Currently, stdlib has a limited set of dedicated "async" APIs for performing various utility operations. The goal of this idea is to achieve feature parity with [async.js](https://caolan.github.io/async/v3/), a popular library providing callback-based async APIs.

Motivation for this idea stems from certain advantages afforded by callback-based asynchronous programming. Notable among them is superior performance and the ability to more readily return and inspect status objects.

### Related Issues

Related issues https://github.com/stdlib-js/google-summer-of-code/issues/9

### Questions

No.

### Other

No.

### Checklist

- [x] I have read and understood the [Code of Conduct](https://github.com/stdlib-js/stdlib/blob/develop/CODE_OF_CONDUCT.md).
- [x] Searched for existing issues and pull requests.
- [x] The issue name begins with `RFC:`.

Start by comparing stdlib's existing async APIs with async.js v3 and reading the related Google Summer of Code issue. The issue names no files or tests; completion would require defining and implementing a feature-parity scope across the relevant callback-based APIs.

索引モデルが issue の本文から書いたものです。