Introduce two new Connection::InstanceSource subclasses in PEP249.qll:
- ConnectionGetterAttributeRead: recognises self._conn reads inside
getter methods of classes whose __init__ stores a connect() call in
that attribute. The AttrRead node coincides with the return node, so
the existing TypeTracker returnStep propagates the connection type to
all call sites automatically.
- ConnectionConstructorAttributeRead: recognises ClassName()._conn
direct attribute reads on constructor-call results.
Both classes share the classStoresConnectionInInit helper predicate
that checks for the self.attr = dbapi.connect() store pattern in __init__.
Also adds test cases for the new patterns in the hdbcli test suite
and a change note.