Add kotlinp, a tool to print Kotlin metadata in class/module files

At the moment, it's not published anywhere, but that may change soon

 #KT-23198

libraries/tools/kotlinp/testData/NestedClasses.kt

@@ -0,0 +1,16 @@
+interface A {
+    interface B {
+        interface C
+    }
+
+    companion object D {
+        enum class E {
+            E1,
+            E2,
+        }
+
+        sealed class F {
+            class G : F()
+        }
+    }
+}