saip/personalization: add MncLen configurable parameter

Add a new ConfigurableParameter that represents the MNC length
(2 or 3 digits) in EF.AD (Administrative Data).

Change-Id: I6c600faeab00ffb072acbe94c9a8b2d1397c07d3
Co-authored-by: Vadim Yanitskiy <vyanitskiy@sysmocom.de>
Jenkins: skip-card-test

tests/unittests/test_configurable_parameters.py

@@ -267,6 +267,15 @@ class ConfigurableParameterTest(unittest.TestCase):
                                  '11111111111111111111111111111111'
                                  '22222222222222222222222222222222'),
 
+            Paramtest(param_cls=p13n.MncLen,
+                      val='2',
+                      expect_clean_val=2,
+                      expect_val='2'),
+            Paramtest(param_cls=p13n.MncLen,
+                      val=3,
+                      expect_clean_val=3,
+                      expect_val='3'),
+
             ]
 
         for sdkey_cls in (