* Adjust UtilityProcess{Host,Manager} to propagate ipc::LaunchErrors for
their clients, or to create new ones where none previously existed.
* Adjust the various clients of the above to to handle the additional
information -- mostly by adding the additional failure-location data
to log messages.
* Fix an unrelated bug wherein the return type of `LaunchProcess` was
declared as exclusive, despite being cached and reused.
In particular, filedialog::Error objects should now contain -- and report
to telemetry without further adjustment -- the actual error code from
`ipc::LaunchError`s.
(Reporting the original failure location as well will occur in bug
1884221.)
Differential Revision: https://phabricator.services.mozilla.com/D209715
