Bug 1895375 - [4/4] Propagate ipc::LaunchErrors to callers r=ipc-reviewers,nika

* 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