Debugger, BE: Provide Java-like stepping for 'for' loops

- Visit '}' instead of 'for' keyword on post-condition
- Visit 'for' keyword on pre-condition

compiler/testData/debug/localVariables/destructuringInFor.kt

@@ -16,5 +16,4 @@ fun box() {
 // TestKt:7: map:java.util.Collections$SingletonMap
 // TestKt:9: map:java.util.Collections$SingletonMap, a:java.lang.String, b:java.lang.String
 // TestKt:7: map:java.util.Collections$SingletonMap
-// TestKt:8: map:java.util.Collections$SingletonMap
 // TestKt:11: map:java.util.Collections$SingletonMap