force a11y and manually manage atspi helpers

- options to launcher crash on ubuntu, instead set QT_ env vars to force
  a11y (only in test helper so chances are low that the atspi helpers get
  dbus invoked)
- spawn atspi registry in addition to the launcher
- manually send kill to both the launcher and the registryd to prevent
  process leakage in noisolation (i.e. CI) use cases