[v14.x backport] stream: accept iterable as a valid first argument
Backport of https://github.com/nodejs/node/pull/36479
Followed instructions in How to Backport a Pull Request to a Release Line
Motivation: Getting https://github.com/DefinitelyTyped/DefinitelyTyped/pull/49868 merged for Node 14, to make the types there reflect what's been in the documentation for Node.js since Node.js 13.10