Normalise prop types of mapped components with ArrayValue

[axelboc]

From #1738 (comment)

The value, auxValues, errors, auxErrors and axisValues props of mapped components (MappedLineVis, MappedRgbVis, etc.) were typed in a few different, inconsistent ways:

• with NumArray (= number[] | TypedArray)
• with ArrayValue<DType> (where DType matches the one of the dataset prop — e.g. Dataset<ArrayShape, NumericType> => ArrayValue<NumericType>, but it works with any other dtype or dtype union like NumericLikeType)
• with Value<Props['dataset']> to avoid duplicating the dtype.

While the third way is the most robust and DRY, it's not the most readable since it adds an extra level of misdirection. And while the first way is the most explicit, it becomes less readable and/or more error-prone with other dtypes, like NumericLikeType, PrintableType or ComplexType (especially once we start supporting big ints).

So I'm going for the middle ground with ArrayValue.

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While I'm at it:

• I remove NumArrayDataset completely, which was an alias for Dataset<ArrayShape, NumericType>; it adds a couple of imports in a few files, but it's less confusing, especially since we don't have aliases for datasets with other dtypes, like Dataset<ArrayShape, NumericLikeType>.
• I rename Primitive to ScalarValue. This makes it clearer that ScalarValue is the value of datasets with ScalarShape.

[loichuder]

Not bad! Yeah I think it improves things