[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/builtinsSerializer/annotationArguments/string.kt

@@ -0,0 +1,12 @@
+package test
+
+annotation class JustString(val string: String)
+
+annotation class StringArray(val stringArray: Array<String>)
+
+@JustString("kotlin")
+@StringArray(arrayOf())
+class C1
+
+@StringArray(arrayOf("java", ""))
+class C2