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/UseKotlinInner.kt

@@ -0,0 +1,19 @@
+package test
+
+private open class KotlinClass : KotlinInterface.KotlinInner2() {
+
+    inner class KotlinInner
+
+}
+
+private interface KotlinInterface {
+    open class KotlinInner2 : JavaClass2() {
+        class KotlinInner3
+    }
+}
+
+private fun getKotlinInner() = UseKotlinInner().kotlinInner
+
+private fun getJavaInner() = UseKotlinInner().javaInner
+
+private fun getKotlinInner3() = UseKotlinInner().kotlinInner3