Share change ticks between systems

## What problem does this solve or what need does it fill?

Sometimes you want to add the transform propagation systems to the schedule in multiple places. The transform systems use change detection to not propagate transforms that haven't changed. This will do extra work because the propagation will run for any transforms changed since the current system has run instead of transforms changed since the last time any transform propagation has run.

## What solution would you like?

Probably some type of `AtomicTicks` and `AtomicSystem` that are passed in `System::run`. This is a little tricky since you'd have to clone instances of the system when adding them. For Transform propagation we could potentially store the systems on the Plugin.

## What alternative(s) have you considered?

I was also thinking of an ArcSystem, but I don't think that can work without locking since we take mutable access to a system to update it's archetypes.