PY-14617 Update references to modules imported via relative imports inside the moved module

Current solution is very crude, because we can't use standard IDE
facilities to find usages of the import element in the a file, once
that file was moved. And exactly that API MoveFileHandler offers to us.

python/testData/refactoring/move/usagesOfUnqualifiedOldStyleRelativeImportsInsideMovedModule/after/src/m1.py

@@ -0,0 +1,5 @@
+import pkg.m2
+import pkg.subpkg.m3
+
+
+print(pkg.m2, pkg.subpkg.m3.VAR)

python/testData/refactoring/move/usagesOfUnqualifiedOldStyleRelativeImportsInsideMovedModule/after/src/pkg/m2.py

@@ -0,0 +1 @@
+VAR = 42

python/testData/refactoring/move/usagesOfUnqualifiedOldStyleRelativeImportsInsideMovedModule/before/src/pkg/m1.py

@@ -0,0 +1,5 @@
+import m2
+import subpkg.m3
+
+
+print(m2, subpkg.m3.VAR)

python/testData/refactoring/move/usagesOfUnqualifiedOldStyleRelativeImportsInsideMovedModule/before/src/pkg/m2.py

@@ -0,0 +1 @@
+VAR = 42