Cache merged dynamic and static data

[jacomyal]

Right now, dynamic edges and nodes data seem to be properly cached, but components have to merge them with the static data themselves, using mergeStaticDynamicData.

This helper function is not free, and is called very often in various places, such as:

• Node.tsx and Edge.tsx
• RangeFilter.tsx and TermsFilter.tsx
• Selection.tsx (which itself then calls Node.tsx and/or Edge.tsx)

We probably could cache the merged items data, to prevent having to reproduce these merged collections all the time.