Abstract values fetching out of mapped vis components

[axelboc]

First, I created a VisBoundary component to hold the ErrorBoundary and Suspense logic of the vis containers. I did not end up moving the DimensionMapper into this component, as keeping the mapper in the containers means I could use VisBoundary in the RawVisContainer and ScalarVisContainer and remove ErrorBoundary and Suspense from Visualizer.

Second, I moved all the data fetching (useDatasetValue(s)) out of the mapped visualizations and inside two new components: ValueFetcher and NxValuesFetcher. I used the render props pattern, as it is much clearer than my previous state-based solution.

Third, I refactored the way we pass formatters to ScalarVis and MatrixVis. Instead of having a guard and an early return in the mapped vis components, I decided to make use of simple type casting.

Fourth, I ran ts-prune to remove unused exports, notably in guards.ts.

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What's next

• Move prefetching to NxValuesFetcher so retrying a cancelled NeXus visualization doesn't lead to a refetching waterfall.
• [Can wait] Review current solution for complex visualizations (containers, mapped vis, typings, etc.)
• [Can wait] Review mapped vis components to see if anything else can be abstracted out of them.

[loichuder]

I wasn't sold on the concept but as usual, implementation trumps intuition.

I like the fact that one can write a new fetcher and then use the render props to distribute the values around to the children component as it is done by NeXus.