[Fix] Fix NDArray single-arg subscript crash

NdarrayType.__class_getitem__ crashed when called with a single arg
(e.g. NdarrayType[dtype]) because it tried to unpack a non-tuple.
Wrap single args in a tuple before passing to __init__.

Author: hughperkins

python/quadrants/types/ndarray_type.py

@@ -94,8 +94,10 @@ def __init__(
         self.boundary = int(to_boundary_enum(boundary))
 
     @classmethod
-    def __class_getitem__(cls, args, **kwargs):
-        return cls(*args, **kwargs)
+    def __class_getitem__(cls, args):
+        if not isinstance(args, tuple):
+            args = (args,)
+        return cls(*args)
 
     def check_matched(self, ndarray_type: NdarrayTypeMetadata, arg_name: str):
         # FIXME(Haidong) Cannot use Vector/MatrixType due to circular import