This merge request is Phase 1 of several to implement the distributed parallel
contour tree in VTKm. This merge requests adds the base outline for the
algorithm. The implementation of the details of the algorithm in the
BoundaryRestrictedAugmentedContourTree.h is currently still missing.
However, these will require a substantial (~3000) lines of additional code.
The goal is to stage the integration process across merge requests to make
the review process simpler.
Now that the dispatcher does its own TryExecute, filters do not need to
do that. This change requires all worklets called by filters to be able
to execute without knowing the device a priori.
