The recent removal of type selectors in ControlSignature field tags
means that the BenchmarkFieldAlgorithms code was creating code paths
that were never followed and lead to impossible type conversions (e.g.
Vec to float). Fixed the problem by specifing the types for the
VariantArrayHandles better.
Rather than force all dispatchers to be templated on a device adapter,
instead use a TryExecute internally within the invoke to select a device
adapter.
Because this removes the need to declare a device when invoking a
worklet, this commit also removes the need to declare a device in
several other areas of the code.
