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/classObject/Delegation.kt

@@ -5,7 +5,7 @@ trait T {
 }
 
 class A : T {
-    override fun foo() = 42
+    override fun foo(): Int = 42
 
     class object : T by A()
 }