add SimulationData type

[axsk]

This is nagging me for a long time and has caused a lot of headaches.

The main problem is that each of these can stand on their own, no clear hierarchy is obvious.

ISOKANN has its own trainings data, which however can differ from the full "coordinate" data.
For visualization however it needs access to the "coordinate" data.
Adaptive sampling complicates this further.

One way of patching them together is via a DataLoader which doubles as data provider for ISOKANN but also holds raw data, and is able to also contain a Simulation.

Where do we attach known reaction coordinates (for visualization) etc?

[axsk]

Iso needs to know only data. data can be either the common tuple of arrays, or some other struct implementing the MLUtils.getobs interface. In the latter case it could host a simulation. Iso can just tell data to resample itself, and data can forward to simulation.
I think this also makes the most sense semantically.

[axsk]

A good starting point would be a type SimulationData which holds the simulation coords (necessary for output), the isokann data (possibley transformed) and the sim object to generate the data.

This should then be able to work as data object for Iso2.

[axsk]

We could make this an interface as well. Here some thoughts on the specs.

getobs or getdata?
getxs
getys

getcoords (but how do we return the ys coords)

dim
outdim? (chi dimension)
length?
getindex? (but calling only via getobs)
gpu/cpu?