RUSTSEC-2025-0024: sync::mpsc: prevent double free on `Drop`

RUSTSEC-2025-0024: sync::mpsc: prevent double free on `Drop`

This PR is fixing a regression introduced by #121646 that can lead to a
double free when dropping the channel.

The details of the bug can be found in the corresponding crossbeam PR
https://github.com/crossbeam-rs/crossbeam/pull/1187

Signed-off-by: Petros Angelatos <petrosagg@gmail.com>
FG: cherry-pick from upstream b9e2ac5c7b1d6bb3b6f5fdfe0819eaf7e95bf7ff
FG: drop test context
Signed-off-by: Fabian Grünbichler <git@fabian.gruenbichler.email>
Gbp-Pq: Topic upstream
Gbp-Pq: Name RUSTSEC-2025-0024-sync-mpsc-prevent-double-free-on-Drop.patch