There's a very sloppy registrar-actor-bootup syncing approach used in
this fixture (basically just guessing how long to sleep to wait for it
to init and bind the registry socket) using a `global _PROC_SPAWN_WAIT`
that needs to be made more reliable. But, for now i'm just playing along
with what's there to try and make less CI runs flaky by,
- sleeping *another* 1s when run from non-linux CI.
- reporting stdout (if any) alongside stderr on teardown.
- not strictly requiring a `proc.returncode == -2` indicating successful
graceful cancellation via SIGINT; instead we now error-log and only
raise the RTE on `< 0` exit code.
* though i can't think of why this would happen other then an
underlying crash which should propagate.. but i don't think any test
suite does this intentionally rn?
* though i don't think it should ever happen, having a CI run
"error"-fail bc of this isn't all that illuminating, if there is
some weird `.returncode == 0` termination case it's likely not
a failure?
For later, see the new todo list; we should sync to some kind of "ping"
polling of the tpt address if possible which is already easy enough for
TCP reusing an internal closure from `._root.open_root_actor()`.