Use actions instead of write boolean for data transfers

runtime/pairs.cpp

runtime/pairs.hpp

runtime/pairs_common.hpp

runtime/thermo.hpp

runtime/vtk.hpp

src/pairs/code_gen/cgen.py

src/pairs/ir/actions.py

src/pairs/ir/device.py

src/pairs/ir/kernel.py

src/pairs/ir/module.py

src/pairs/transformations/devices.py