fs: add FileHandle.prototype.readableWebStream()

Adds an experimental `readableWebStream()` method to `FileHandle` that
returns a web `ReadableStream`

Signed-off-by: James M Snell <jasnell@gmail.com>

PR-URL: https://github.com/nodejs/node/pull/39331


Reviewed-By: Robert Nagy <ronagy@icloud.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>