appview/pipelines/ssh: add ssh server to appview to stream logs
this change introduces an ssh server to the appview. this server is
backed by a charmbracelet/wish app. it is invoked like so:
ssh -t appview.host -p 3333 at://.../sh.tangled.pipeline/...
the wish app then opens up a TUI for that pipeline job, with live
streaming of logs and statuses for all workflows in that pipeline
(available a separate tabs).
at startup, the appview needs to currently be run with
TANGLED_SSH_ENABLED=true, which starts the ssh server on 0.0.0.0:3333 by
default.
Signed-off-by: oppiliappan <me@oppi.li>