tests: Add tests to improve coverage of py/objtype.c.

tests/basics/sys_getsizeof.py

@@ -0,0 +1,15 @@
+# test sys.getsizeof() function
+
+import sys
+try:
+    sys.getsizeof
+except AttributeError:
+    print('SKIP')
+    raise SystemExit
+
+print(sys.getsizeof([1, 2]) >= 2)
+print(sys.getsizeof({1: 2}) >= 2)
+
+class A:
+    pass
+print(sys.getsizeof(A()) > 0)