Added a test for resolving from a Python *.pyi stub to a Python file (PY-16402)

python/testData/pyi/resolve/fromPyiToClassInPy/FromPyiToClassInPy.pyi

@@ -0,0 +1,5 @@
+from m1 import C
+
+
+def f(x: C) -> None: ...
+#        <ref>

python/testData/pyi/resolve/fromPyiToClassInPy/m1.py

@@ -0,0 +1,2 @@
+class C:
+    pass

python/testSrc/com/jetbrains/python/pyi/PyiResolveTest.java

@@ -35,4 +35,8 @@ public class PyiResolveTest extends PyMultiFileResolveTestCase {
   public void testBuiltinInt() {
     assertResolvesTo(PyClass.class, "int");
   }
+
+  public void testFromPyiToClassInPy() {
+    assertResolvesTo(PyClass.class, "C");
+  }
 }