Rather than try to collect all `LastCell` types inside of a single
header and make an uber type, have each cell locator define its own cell
locator type and use that.
Deprecated the `CellLocator` class and made all methods of the
other `CellLocator` classes non-virtual. General locators can
still use the `CellLocatorGeneral` class, but this class now
only works with a predefined set of locators. (The functionality
to provide a function to select a locator has been removed.)
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.
These changes caused some warnings in clang to show up based on virtual
methods in other cell locators. Hence, the rest of the cell locators
have also had some of their code moved to vtkm_cont.
