Rename: Use qualified class name when looking for occurrences in non-code files

#KT-14128 Fixed
 #KT-13862 Fixed
 #KT-6199 Fixed

idea/testData/refactoring/rename/classUsagesInTextFiles/before/dummy.txt

@@ -0,0 +1,3 @@
+C
+A.B.C
+test.A.B.C

idea/testData/refactoring/rename/classUsagesInTextFiles/before/test/test.kt

@@ -0,0 +1,9 @@
+package test
+
+class A {
+    private class B {
+        class /*rename*/C {
+
+        }
+    }
+}