The newer version of `ArrayHandle` no longer supports different types of
portals for different devices. Thus, the `ReadPortalType` and
`WritePortalType` are sufficient for all types of portals across all
devices.

This significantly simplifies supporting execution objects on devices,
and thus this change also includes many changes to various execution
objects to remove their dependence on the device adapter tag.

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.

Also fix deadlocks that occur when portals are not destroyed
in time.

Marked the old versions of PrepareFor* that do not use tokens as
deprecated and moved all of the code to use the new versions that
require a token. This makes the scope of the execution object more
explicit so that it will be kept while in use and can potentially be
reclaimed afterward.

This work updates Gunther Contour tree work to be parallel.
With contributions from: @oruebel, @dcamp and @sujin.philip.