Add SVE nontemporal stores and scatters, including masked variants

.gitlab-ci.yml

src/pystencils/backends/arm_instruction_sets.py

src/pystencils/backends/cbackend.py

src/pystencils/backends/simd_instruction_sets.py

tests/test_conditional_vec.py

tests/test_random.py

tests/test_vectorization.py

tests/test_vectorization_specific.py