Add `GetNumberOfComponentsFlat` method to `ArrayHandle`

Getting the number of components (or the number of flattened components) from an ArrayHandle is usually trivial. However, if the ArrayHandle is special in that the number of components is specified at runtime, then it becomes much more difficult to determine.

Getting the number of components is most important when extracting component arrays (or reconstructions using component arrays) with UnknownArrayHandle. Previously, UnknownArrayHandle used a hack to get the number of components, which mostly worked but broke down when wrapping a runtime array inside another array such as ArrayHandleView.

To prevent this issue, the ability to get the number of components has been added to ArrayHandle proper. All Storage objects for ArrayHandles now need a method named GetNumberOfComponentsFlat. The implementation of this method is usually trivial. The ArrayHandle template now also provides a GetNumberOfComponentsFlat method that gets this information from the Storage. This provides an easy access point for the UnknownArrayHandle to pull this information.