[K2/N] Add klib contents serialization tests from old testinfra

Merge-request: KT-MR-8509
Merged-by: Vladimir Sukharev <Vladimir.Sukharev@jetbrains.com>

native/native.tests/testData/klibContents/builtinsSerializer/simple.txt

@@ -0,0 +1,6 @@
+    class Class constructor() {
+        fun member(): Nothing?
+    }
+    fun <T> T.extension(): T?
+    fun function(int: Int, string: String = ...): Class
+    val property: Unit