Geometry updates via signals

As discussed with @schmidtp, maybe we should switch to sending signals for new geometries instead of having subscribers monitor full geometry device (which, I believe, happens even when you just monitor a single property).

What I've just tested a bit:

1. ✅ updating geometry on geometry device, receiving it on assemblers
2. ✅ geometry device already up, bring up pipeline (manager asks geometry device to send signal after assemblers are up)
3. ⬜ subscribers already up, instantiate geometry device

Issue with 3.: apparently, the [signal].connected is not populated when onInitialization is called. You'll note I for now added a await sleep(1) which seems sufficient - should we bother Karabo people about what the correct way is or does someone in calibration have more signal experience?