[KLIB][tests] Reorganize "klib dump-metadata" tests

- Keep the test data under "native/native.tests/testData/klib/" dir
- Rename tests from "klib contents" to "klib dump-metadata"

native/native.tests/testData/klib/dump-metadata/data_class.kt

@@ -0,0 +1,11 @@
+// MUTED_WHEN: K1
+package test
+
+data class DataClass(
+    val intProp: Int,
+    val stringProp: String
+) {
+    val nonConstructorProp: Int = 0
+}
+
+data object DataObject