stream/iter `elastic` backpressure policy proposal

[jasnell]

@nodejs/quic @nodejs/streams @trivikr @mcollina ... just a heads up for a proposal to add another backpressure policy for stream/iter ... WinterTC55/iter-streams#20

[trivikr]

I think this issues can be closed as it was created as an FYI.

The spec was updated in WinterTC55/iter-streams#23, and the PR in Node.js is up at #64464

[jasnell]

This can be closed