Remove some legacy codegen tests, move some to generated

compiler/testData/codegen/box/when/multipleEntries.kt

@@ -0,0 +1,12 @@
+fun foo(x: Any) =
+        when (x) {
+            0, 1 -> "bit"
+            else -> "something"
+        }
+
+fun box(): String {
+    if (foo(0) != "bit") return "Fail 0"
+    if (foo(1) != "bit") return "Fail 1"
+    if (foo(2) != "something") return "Fail 2"
+    return "OK"
+}