AST-1293 Upsample: Use new DPBuffer unique_ptr/xtensor interface
Update all process methods and calls within Upsample to the new unique_ptr DPBuffer interface. Use xtensor instead methods in place of casacore ones when interacting with DPBuffer.
Update all process methods and calls within Upsample to the new unique_ptr DPBuffer interface. Use xtensor instead methods in place of casacore ones when interacting with DPBuffer.