contrib.psycopg: Patch all imports of register_type

`register_type` was patched in #96, though only in psycopg.extensions.
The function is defined in psycopg2._psycopg and imported in psycopg2._json
neither of them are patched and if used cause a TypeError.

Author: Stefan Tjarks

ddtrace/contrib/psycopg/patch.py

@@ -99,4 +99,10 @@ def _unroll_args(obj, scope=None):
     (psycopg2.extensions.register_type,
      psycopg2.extensions, 'register_type',
      _extensions_register_type),
+    (psycopg2._psycopg.register_type,
+     psycopg2._psycopg, 'register_type',
+     _extensions_register_type),
+    (psycopg2._json.register_type,
+     psycopg2._json, 'register_type',
+     _extensions_register_type),
 ]

tests/contrib/psycopg/test_psycopg.py

@@ -115,6 +115,11 @@ def test_manual_wrap_extension_types(self):
         #   TypeError: argument 2 must be a connection, cursor or None
         extras.register_uuid(conn_or_curs=conn)
 
+        # NOTE: this will crash if it doesn't work.
+        #   _ext.register_default_json(conn)
+        #   TypeError: argument 2 must be a connection, cursor or None
+        extras.register_default_json(conn)
+
     def test_connect_factory(self):
         tracer = get_dummy_tracer()