Fetch whole dataset only when autoScale is off (and slices otherwise)

[loichuder]

Improvement for #616

Also:

• Enforce numeric types for complex fields
• Remove persistence of autoScale

Drafting it for discussion as I feel we can do better here:

• There is a lot of common behaviour in the various LineVis containers that we could refactor
• I liked that fact that useLineConfig was always used in Mapped components but now, I need it outside...

[axelboc]

Apart from the loading message logic, which can be moved inside VisBoundary, I don't see a lot of duplication between the line and spectrum containers. Where there's more duplication now is between the line and heatmap containers. However, I don't see it as a problem, as all the business logic is nicely encapsulated in shared hooks and components.

Comparing the containers, I've actually just noticed that we have duplicate NeXus type guards: assertNumericNxData and assertNumericSignal, and assertComplexNxData and assertComplexSignal.

The fact that we use useLineConfig in the containers can indeed feel like we're breaking one of our design decisions, but perhaps this wasn't a great decision in the first place. It makes sense that the user's preferences would eventually affect the fetching of the data somehow. Perhaps relaxing this decision will open the door to some refactoring to reduce duplication/complexity in the mapped vis components?

[axelboc]

nice!

[loichuder]

/approve