Merge branch 'backend-rework' into fhennig/pragmas

src/pystencils/backend/ast/analysis.py

src/pystencils/backend/transformations/canonical_clone.py

src/pystencils/backend/transformations/reshape_loops.py

src/pystencils/types/types.py

tests/nbackend/test_extensions.py

tests/nbackend/transformations/test_reshape_loops.py