Remove Tandem.GroupTandem and previous state pattern

[samreid]

From phetsims/tandem#87, we need to eliminate usages of createGroupTandem. Things should be converted to use PhetioGroup if necessary. I'll follow the instrumentation guide:

Here is an ordered list of how to approach instrumenting an element that is dynamically created:

1. Does it even need instrumentation? Often instances don't need to be instrumented, or can perhaps be instrumented as a component of their parent (instead of being instrumented themselves)
2. Can it be created eagerly? Allocating dynamic elements on startup simplifies the instrumentation process, especially
   when supporting PhET-iO state and API validation.
3. Instrument the object dynamically, using PhetioGroup or PhetioCapsule. Use PhetioCapsule for single dynamic
   instances. Use PhetioGroup for multiple instances of the same type. If you have a use case that is not addressed by one or both of those, then please consult with the PhET-iO subteam, and potentially create a new IO Type suitable for your simulation.

[samreid]

I reached out to @jessegreenberg on slack to ask if there is ongoing development in this repo that requires coordination.

[samreid]

Fixed in the commits. Once I saw an error like "description should be different if something has changed"? in the state wrapper but I couldn't replicate it.

This sim is listed in the "Upgrade to Studio" goals for instrumentation, I think that will be an appropriate time for improvements, if necessary. But this seems good enough to close. @zepumph reopen if you recommend a review.