Merge branch 'backend-rework' into fhennig/sycl

mypy.ini

src/pystencils/__init__.py

src/pystencils/backend/ast/analysis.py

src/pystencils/backend/ast/iteration.py

src/pystencils/backend/ast/structural.py

src/pystencils/backend/emission.py

src/pystencils/backend/kernelcreation/cpu_optimization.py

src/pystencils/backend/kernelcreation/typification.py

src/pystencils/backend/transformations/__init__.py

src/pystencils/backend/transformations/add_pragmas.py

src/pystencils/backend/transformations/canonical_clone.py

src/pystencils/backend/transformations/eliminate_branches.py

src/pystencils/config.py

src/pystencils/kernelcreation.py

src/pystencils/types/types.py

tests/nbackend/kernelcreation/test_openmp.py

tests/nbackend/test_ast.py

tests/nbackend/test_extensions.py

tests/nbackend/transformations/test_add_pragmas.py

tests/nbackend/transformations/test_branch_elimination.py