Tools › Start SSH Session ran the system `ssh -t` in a terminal, which never
used the password saved in the SSH configuration and, on Windows, could not
take a typed password either.
The session now opens a login shell over the IDE's SSH connection: the
terminal manager can attach a channel (here an SSH shell) next to local PTYs,
with the same output batching, UTF-8 decoding and exit events. A password or
passphrase that isn't saved is asked for in a dialog, and an unknown host key
asks to be trusted, before reconnecting. Closing the tab hangs the shell up.
Also: a remote process closed by this side now ends without waiting for a
close that russh never forwards, and each connection attempt gets its own IPC
channel, since a failed attempt invalidates the one it was given.
Fixes#2874
l0ng-ai
76faa39bc5