dataflow: do not treat fields with qualified this as effectively unqualified (IDEA-99722)

java/java-tests/testData/inspection/dataFlow/fixture/EffectivelyUnqualified.java

@@ -0,0 +1,12 @@
+abstract class Foo {
+  protected String bar;
+}
+
+class FF extends Foo {
+  class FFI extends Foo {
+    void f() {
+      if (this.bar == FF.this.bar);
+      if (<warning descr="Condition 'this.bar == FFI.this.bar' is always 'true'">this.bar == FFI.this.bar</warning>);
+    }
+  }
+}