Refactor WorkletMapTopology for clarity.

Ref #374 (closed).

The From and To nomenclature for topology mapping has been confusing for both users and developers, especially at lower levels where the intention of mapping attributes from one element to another is easily conflated with the concept of mapping indices (which maps in the exact opposite direction).

These identifiers have been renamed to VisitTopology and IncidentTopology to clarify the direction of the mapping. The order in which these template parameters are specified for WorkletMapTopology have also been reversed, since eventually there may be more than one IncidentTopology, and having IncidentTopology at the end will allow us to replace it with a variadic template parameter pack in the future.

The convenience implementations of WorkletMapTopology have been renamed for clarity as follows:

WorkletMapPointToCell --> WorkletVisitCellsWithPoints
WorkletMapCellToPoint --> WorkletVisitPointsWithCells

The old names will still work as we figure out a deprecation mechanism.

The ControlSignature tags have been renamed as follows:

FieldInTo --> FieldInVisit
FieldInFrom --> FieldInMap
FromCount --> IncidentElementCount
FromIndices --> IncidentElementIndices