[3.13] gh-136234: Fix `SelectorSocketTransport.writelines` to be robust to connection loss (GH-136743) (GH-138702) (#139710)

[3.14] gh-136234: Fix `SelectorSocketTransport.writelines` to be robust to connection loss (GH-136743) (GH-138702)
(cherry picked from commit 5cd6cfe4cf6770b9424bb23f8c7c661f7a3db7b0)

Co-authored-by: Kumar Aditya <kumaraditya@python.org>