Don't use Cython resolver for resolving references to __init__.py (PY-13554, PY-14102)

Normal resolvers should do their job with __init__.py. Using the Cython
resolver instead resulted in bypassing class type to instance type
casting for docstring type references to classses in nested packages.

python/testData/inspections/PyUnresolvedReferencesInspection/DocstringTypeFromSubModule/a.py

@@ -0,0 +1,12 @@
+from pkg1 import C
+
+
+def foo():
+    """
+    :rtype: pkg1.C
+    """
+    return C(0)
+
+
+obj = foo()
+obj.bar

python/testData/inspections/PyUnresolvedReferencesInspection/DocstringTypeFromSubModule/pkg1/__init__.py

@@ -0,0 +1 @@
+from m1 import *

python/testData/inspections/PyUnresolvedReferencesInspection/DocstringTypeFromSubModule/pkg1/m1.py

@@ -0,0 +1,6 @@
+class C(object):
+    def __init__(self, bar):
+        """
+        :param int bar: Some parameter
+        """
+        self.bar = bar

python/testSrc/com/jetbrains/python/inspections/PyUnresolvedReferencesInspectionTest.java

@@ -410,6 +410,11 @@ public class PyUnresolvedReferencesInspectionTest extends PyInspectionTestCase {
     myFixture.checkHighlighting(isWarning(), isInfo(), isWeakWarning());
   }
 
+  // PY-13554
+  public void testDocstringTypeFromSubModule() {
+    doMultiFileTest();
+  }
+
   @NotNull
   @Override
   protected Class<? extends PyInspection> getInspectionClass() {