Add explicit return types to several test data files so that AST access is not needed

Test cases are chosen so that addition/removal of explicit type will not interfere with the original purpose of the test

compiler/testData/loadJava/compiledKotlin/fun/nonGeneric/ExtFunInClass.kt

@@ -1,5 +1,5 @@
 package test
 
 class ExtFunInClass {
-    fun Int.shuffle() = 1
+    fun Int.shuffle(): Int = 1
 }