[Test] Add ability to specify applicability of diagnostic to module or file

compiler/testData/foreignAnnotations/tests/aosp.kt

@@ -1,4 +1,5 @@
 // !DIAGNOSTICS: -UNUSED_VARIABLE -UNUSED_PARAMETER
+// SOURCE_RETENTION_ANNOTATIONS
 // FILE: A.java
 
 import com.android.annotations.*;
@@ -21,7 +22,6 @@ public class A<T> {
 }
 
 // FILE: main.kt
-// SOURCE_RETENTION_ANNOTATIONS
 
 fun main(a: A<String>, a1: A<String?>) {
     a.foo("", null)?.length