Test built-ins serializer, untie built-ins from class loader resources

compiler/testData/serialization/simple.kt

@@ -0,0 +1,11 @@
+package test
+
+class Class {
+    fun member() = null
+}
+
+fun function(int: Int, string: String = "default"): Class
+
+fun <T> T.extension(): T?
+
+val property: Unit

compiler/testData/serialization/simple.txt

@@ -0,0 +1,10 @@
+package test
+
+internal val property: kotlin.Unit
+internal fun function(/*0*/ int: kotlin.Int, /*1*/ string: kotlin.String = ...): test.Class
+internal fun </*0*/ T> T.extension(): T?
+
+internal final class Class {
+    public constructor Class()
+    internal final fun member(): kotlin.Nothing?
+}