[THRIFT-5314][THRIFT-4101] Generate enums that don't error on unexpected values (#2337)

Client: rs
diff --git a/test/rs/src/bin/test_server.rs b/test/rs/src/bin/test_server.rs
index 74be12d..c1f3175 100644
--- a/test/rs/src/bin/test_server.rs
+++ b/test/rs/src/bin/test_server.rs
@@ -268,15 +268,15 @@
     ) -> thrift::Result<BTreeMap<UserId, BTreeMap<Numberz, Insanity>>> {
         info!("testInsanity({:?})", argument);
         let mut map_0: BTreeMap<Numberz, Insanity> = BTreeMap::new();
-        map_0.insert(Numberz::Two, argument.clone());
-        map_0.insert(Numberz::Three, argument);
+        map_0.insert(Numberz::TWO, argument.clone());
+        map_0.insert(Numberz::THREE, argument);
 
         let mut map_1: BTreeMap<Numberz, Insanity> = BTreeMap::new();
         let insanity = Insanity {
             user_map: None,
             xtructs: None,
         };
-        map_1.insert(Numberz::Six, insanity);
+        map_1.insert(Numberz::SIX, insanity);
 
         let mut ret: BTreeMap<UserId, BTreeMap<Numberz, Insanity>> = BTreeMap::new();
         ret.insert(1, map_0);