[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/inners/CurrentPackageAndInner.kt

@@ -0,0 +1,26 @@
+// FIR_IDENTICAL
+// FILE: a/x.java
+package a;
+
+public class x {
+
+    public b getB() { return null; }
+
+    public class b {
+        public b getB() { return null; }
+    }
+
+}
+
+// FILE: a/b.java
+package a;
+
+public class b {}
+
+// FILE: test/test.kt
+package test
+
+import a.x
+
+fun test() = x().getB()
+fun test2() = test().getB()