Adapt field parameter collection to changes in pystencils.

src/pystencilssfg/extensions/sycl.py

src/pystencilssfg/ir/__init__.py

src/pystencilssfg/ir/postprocessing.py

src/pystencilssfg/ir/source_components.py

tests/generator_scripts/expected/Variables.h

tests/ir/test_postprocessing.py