Implement DynamicFunction, that can be passed as a parameter/template to the kernel

src/pystencils_autodiff/_backport.py

src/pystencils_autodiff/framework_integration/astnodes.py

src/pystencils_autodiff/framework_integration/printer.py

src/pystencils_autodiff/framework_integration/types.py

tests/test_dynamic_function.py