When by String constants:

Generate TABLESWITCH/LOOKUPSWITCH bytecode operation for when operator by String constants

compiler/testData/codegen/bytecodeText/whenStringOptimization/statement.kt

@@ -0,0 +1,19 @@
+fun foo1(x : String) : String {
+    when (x) {
+        "abc", "cde" -> return "abc_cde"
+        "efg", "ghi" -> return "efg_ghi"
+    }
+
+    return "other"
+}
+
+fun foo2(x : String) : String {
+    when (x) {
+        "abc", "cde" -> return "abc_cde"
+        "efg", "ghi" -> return "efg_ghi"
+        else -> return "other"
+    }
+}
+
+// 2 LOOKUPSWITCH
+