[JS IR] Adapt stepping tests for Kotlin/JS

compiler/testData/debug/stepping/whenComplicatedSubject.kt

@@ -21,7 +21,7 @@ fun box() {
 // The JVM_IR backend optimizes the inner when to a switch and therefore goes directly to the
 // right case without stepping through evaluation of each condition.
 
-// EXPECTATIONS
+// EXPECTATIONS JVM JVM_IR
 // test.kt:16 box
 // test.kt:5 foo
 // test.kt:6 foo
@@ -32,7 +32,7 @@ fun box() {
 // test.kt:5 foo
 // EXPECTATIONS JVM
 // test.kt:6 foo
-// EXPECTATIONS
+// EXPECTATIONS JVM JVM_IR
 // test.kt:7 foo
 // test.kt:4 foo
 // test.kt:13 foo
@@ -41,9 +41,22 @@ fun box() {
 // EXPECTATIONS JVM
 // test.kt:6 foo
 // test.kt:7 foo
-// EXPECTATIONS
+// EXPECTATIONS JVM JVM_IR
 // test.kt:8 foo
 // test.kt:4 foo
 // test.kt:10 foo
 // test.kt:13 foo
-// test.kt:19 box
+// test.kt:19 box
+
+// EXPECTATIONS JS_IR
+// test.kt:16 box
+// test.kt:6 foo
+// test.kt:10 foo
+// test.kt:11 foo
+// test.kt:17 box
+// test.kt:7 foo
+// test.kt:10 foo
+// test.kt:11 foo
+// test.kt:18 box
+// test.kt:8 foo
+// test.kt:10 foo