src: back snapshot I/O with a std::vector sink

PR-URL: nodejs#46463
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: Ben Noordhuis <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Darshan Sen <[email protected]>
Reviewed-By: Chengzhong Wu <[email protected]>

Author: joyeecheung