[TEST] Migrate duplicating javac tests to new test runners

Also minimize scope of DiagnosticUsingJavac tests to
 `compiler/testData/diagnostics/tests/javac`. This is fine since
 javac compilation mode is still not finished and no one not going to
 support it

compiler/testData/diagnostics/tests/javac/qualifiedExpression/PackageVsRootClass.kt

@@ -0,0 +1,56 @@
+// FIR_IDENTICAL
+// FILE: a/b.java
+package a;
+
+public class b {
+    public void a_b() {}
+}
+
+// FILE: a.java
+public class a {
+    public static class b {
+        public void _ab() {}
+    }
+}
+
+// FILE: some/c1.java
+package some;
+
+public class c1 {
+    public a.b test() { return null; }
+}
+
+
+// FILE: a/c2.java
+package a;
+
+public class c2 {
+    public a.b test() { return null; }
+}
+
+// FILE: c3.java
+public class c3 {
+    public a.b test() { return null; }
+}
+
+// FILE: c1.kt
+package some
+
+fun test() {
+    val a_b = c1().test()
+    a_b.a_b()
+}
+
+// FILE: c2.kt
+package a
+
+fun test() {
+    val a_b = c2().test()
+    a_b.a_b()
+}
+
+// FILE: c3.kt
+fun test() {
+    val _ab = c3().test()
+    _ab._ab()
+}