Remove generated codegen tests, move all testData to box/

A single test file will be generated out of box/ directory

compiler/testData/codegen/box/innerNested/createdNestedInOuterMember.kt

@@ -0,0 +1,14 @@
+fun foo(f: (Int) -> Int) = f(0)
+
+class Outer {
+    class Nested {
+        val y = foo { a -> a }
+    }
+
+    fun bar(): String {
+        val a = Nested()
+        return "OK"
+    }
+}
+
+fun box() = Outer().bar()