Re-introduce and deprecate missing APIs for backward-compatibility.

src/pystencils/_deprecation.py

src/pystencils/backend/emission.py

src/pystencils/backend/kernelcreation/context.py

src/pystencils/backend/kernelcreation/iteration_space.py

src/pystencils/backend/kernelfunction.py

src/pystencils/backend/transformations/add_pragmas.py

src/pystencils/config.py

src/pystencils/kernelcreation.py

src/pystencils/types/meta.py