Introduce experimental -Xuse-javac compilation mode

In this mode, javac AST and Symbol files are used during
Kotlin compilation instead of PSI / binary stuff.
Later, they are reused for Java file compilation.
javac in this mode is integrated into kotlinc.

compiler/testData/compileKotlinAgainstJava/ClassWithNestedEnum.java

@@ -0,0 +1,9 @@
+package test;
+
+public class ClassWithNestedEnum {
+
+    public enum NestedEnum {
+        ONE, TWO, THREE;
+    }
+
+}