doc: add missing `changes:` metadata for recent PRs
Ref: #14636 Ref: #14558
In separate commits because it’s not clear whether both features either get backported to LTS or not backported, and if they are, whether that happens at the same time.
@nodejs/collaborators As a small reminder, try to watch out for this when reviewing API changes :) Also, would be helpful if this could be fast-tracked.