Remove codegen tests with Java, move testData to boxWithJava/

There'll be a single generated test class like
BlackBoxCodegenTestGenerated

compiler/testData/codegen/boxWithJava/functions/removeInIterator.kt

@@ -0,0 +1,13 @@
+fun box() : String {
+    try {
+        removeInIterator.bar(object : Iterator<Int> {
+            public override fun hasNext(): Boolean = false
+            public override fun next(): Int = 1
+        })
+    }
+    catch (e: UnsupportedOperationException) {
+        if (e.getMessage() == "Mutating method called on a Kotlin Iterator")
+            return "OK"
+    }
+    return "fail"
+}