Core: Fix array_of_pointers to act only on those pointers

Previously in array_of_pointers we were updating the vol dict for the
base pointer type.  Now we clone it before modifying it, so we're only
interfering with that one type, not any future types.

Fixes #922

volatility3/framework/objects/utility.py

@@ -44,9 +44,8 @@ def array_of_pointers(
         raise TypeError(
             "Subtype must be a valid template (or string name of an object template)"
         )
-    # We have to clone the pointer class, or we'll be defining the pointer subtype for all future pointers
     subtype_pointer = context.symbol_space.get_type(
         symbol_table + constants.BANG + "pointer"
-    ).clone()
+    )
     subtype_pointer.update_vol(subtype=subtype)
     return array.cast("array", count=count, subtype=subtype_pointer)