Reduce dispatcher template complexity

Initial pass at removing unnecessary template parameters from DispatcherBase and children. The primary change is that DispatcherBase doesn't have an extra template parameter for Device. The result is a minor savings in library size when compiling lots of worklets.

If we can move the DeviceAdapter template off of the Worklet, and instead a parameter of Invoke we might see even more savings, and than Dynamic Array Handle conversion code might not be bound on a per backend basis.