Various GPU-related and some general fixes.

• Recombine KernelWrapper APIs of CPU and GPU JIT
• Clean up JIT module
• Fix kernel constraints analysis
• Fix handling of slices with negative start index
• Fix sparse iteration spaces on GPUs
• Reintroduce GPU periodicity module
• Extend GPU test cases
• Reintroduce kwargs for create_kernel
• Restrict parsing of structured data types to aligned types
• Expose GPU block size selection through CreateKernelConfig

src/pystencils/backend/jit/__init__.py

@@ -26,7 +26,8 @@ Both are available here through `LegacyCpuJit` and `LegacyGpuJit`.
 
 """
 
-from .jit import JitBase, NoJit, KernelWrapper, LegacyCpuJit, LegacyGpuJit
+from .jit import JitBase, NoJit, KernelWrapper
+from .legacy_cpu import LegacyCpuJit
 from .gpu_cupy import CupyJit
 
 no_jit = NoJit()
@@ -38,6 +39,5 @@ __all__ = [
     "LegacyCpuJit",
     "NoJit",
     "no_jit",
-    "LegacyGpuJit",
     "CupyJit",
 ]