Fixing modality in fake overrides

The modality was nondeterministic before.
The main change sits in OverrideResolver: the logic of "fake override" generation is restructured so that
all the descriptors a newly created "fake" one overrides are known by the time it is created, so its
modality can be determined properly from their modalities.

Also, the ReadJavaBinaryClassTestGenerated is now a clear JUnit3 test case

compiler/testData/readJavaBinaryClass/modality/ModalityOfFakeOverrides.java

@@ -0,0 +1,15 @@
+package test;
+
+import java.util.AbstractList;
+
+public class ModalityOfFakeOverrides extends AbstractList<String> {
+    @Override
+    public String get(int index) {
+        return "";
+    }
+
+    @Override
+    public int size() {
+        return 0;
+    }
+}