Some minor internal and API fixes

• Fix wrong legacy imports in alignedarray, simplificationfactory and runhelper.db
• Fix doctests that got broken with numpy 2.0
• Disable graphviz for ASTs (not yet implemented)
• Fix GPU periodicity function usage in data handling
• Expose KernelConstraintsError at top-level

src/pystencils/boundaries/boundaryhandling.py

@@ -36,12 +36,9 @@ class FlagInterface:
         >>> dh = create_data_handling((4, 5))
         >>> fi = FlagInterface(dh, 'flag_field', np.uint8)
         >>> assert dh.has_data('flag_field')
-        >>> fi.reserve_next_flag()
-        2
-        >>> fi.reserve_flag(4)
-        4
-        >>> fi.reserve_next_flag()
-        8
+        >>> assert fi.reserve_next_flag() == 2
+        >>> assert fi.reserve_flag(4) == 4
+        >>> assert fi.reserve_next_flag() == 8
     """
 
     def __init__(self, data_handling, flag_field_name, dtype=DEFAULT_FLAG_TYPE):