Adding an edge from wezterm-ssh -> async_ossl causes the
openssl vendoring feature selection logic to trigger, which
in turn allows `cargo build -p window --examples` to succeed
again on macos.
Since removing the regular periodic background tasks, we're now
prone to not noticing child processes exiting.
This commit explicictly schedules a thread to do that on Windows
so that we can close a tab as soon as it exits.
There are a few notable changes as a result:
* A number of `.ssh/config` options are now respected; host matching
and aliasing and identity file are the main things
* The authentication prompt is inline in the window, rather than
popping up a separate authentication window
Refs: https://github.com/wez/wezterm/issues/457
I can't get this to succeed though; I suspect there may be a lingering
bug from libssh2 and/or trailing support for newer openssh features.
refs: https://github.com/wez/wezterm/issues/457