Scratch: add multifile tests

idea/testData/scratch/when.kts

@@ -0,0 +1,19 @@
+val a = 1
+when(a) {
+    1 -> println("1")
+    else -> println("2")
+}
+
+when(a) {
+    1 -> println("1")
+}
+
+when(a) {
+    2 -> println("2")
+    else -> println("1")
+}
+
+when(a) {
+    1 -> 11
+    else -> 12
+}