Add ETA for simulation completion

[grzanka]

Once simulation enters running state and transports first particles, it is quite straightforward to estimate rate of how many particles per second we can simulate. Based on that and the remaining primaries we can estimate when the simulation will complete and how much time is left till simulation end. That information should be presented to the user.

[DariuszRozmus]

I would like to do this issue

[grzanka]

@DariuszRozmus take a careful look on two types of simulation, one being executed in the browser via Webassembly and another one executed on the Celery queue. Before starting implementation I'd recommend you first deploy locally frontend + backend and submit simple simulation "Proton pencil beam" with SHIELD-HIT12A.

[grzanka]

Lets split this issue into:

• ETA for in-browser Geant4 simulations
• ETA for celery backend simulations
• ETA for Ares simulations