doc: add missing `introduced_in` metadata

Fixes doc build warnings:
```
Failed to add alternative version links to webstreams
Failed to add alternative version links to async_context
```

PR-URL: https://github.com/nodejs/node/pull/39575


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Beth Griggs <bgriggs@redhat.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Michael Dawson <midawson@redhat.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>