Implement the Streams API `ReadableStream`

[oleiade]

As part of our goal to add support for the Streams API to k6 (see #2978), we aim to start by supporting the ReadableStream construct first, as we believe it will be the most valuable and impactful to both our users and our own APIs.

In this context specifically, we aim to make ReadableStream available to our JavaScript runtime (probably imported from k6/streams, or even set as a global object of the runtime), and have support for the ReadableStreamDefaultReader, and ReadableStreamDefaultController as well.

Support for BYOB variants of those constructs is out of scope of this specific issue.

⚠️ This issue has a strong dependency on #3659, and should probably not be closed until it is resolved.