This fixes the `SshSession` being leaked.
There were two leaks:
1. `Arc<SshSession>` itself got leaked into the `SettingsObserver` that
lives as long as the application. Fixed with a weak reference.
2. The two tasks spawned by an `SshSession` had a circular dependency
and didn't exit while the other one was running. Fixed by fixing (1)
and then attaching one of the tasks to the `SshSession`, which means
it gets dropped with the session itself, which leads the other task
to error and exit.
Co-authored-by: Bennet <bennet@zed.dev>
Release Notes:
- N/A
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Co-authored-by: Bennet <bennet@zed.dev>
