for java completion, choose method with most specific return type among same-signature candidates (IDEA-136174)

java/java-tests/testData/codeInsight/completion/normal/ShowMostSpecificOverride.java

@@ -0,0 +1,18 @@
+interface Root1 {
+    A get();
+}
+interface Root2 extends Root1 {
+    B get();
+}
+
+interface Child extends Root1, Root2 {
+}
+
+public class Test {
+    public void test(Child child) {
+        child.get<caret>x
+    }
+}
+
+interface A {}
+interface B extends A {}