Merge bitcoin#20765: fuzz: check that certain script TxoutType are nonstandard

efaf80e fuzz: check that certain script TxoutType are nonstandard (Michael Dietz)

Pull request description:

  - Every transaction of type NONSTANDARD must not be a standard script
  - The only know types of nonstandard scripts are NONSTANDARD and certain NULL_DATA and MULTISIG scripts

  When reviewing bitcoin#20761 I figured this is very similar and might also be good to have

ACKs for top commit:
  MarcoFalke:
    ACK efaf80e

Tree-SHA512: 6f563ee3104ea9d2633aad95f1d003474bea759d0f22636c37aa91b5536a6ff0800c42447285ca8ed12f1b3699bf781dae1e5e0a3362da578749cd3164a06ea4

Author: MarcoFalke

src/test/fuzz/script.cpp

@@ -71,7 +71,15 @@ FUZZ_TARGET_INIT(script, initialize_script)
     (void)IsSolvable(signing_provider, script);
 
     TxoutType which_type;
-    (void)IsStandard(script, which_type);
+    bool is_standard_ret = IsStandard(script, which_type);
+    if (!is_standard_ret) {
+        assert(which_type == TxoutType::NONSTANDARD ||
+               which_type == TxoutType::NULL_DATA ||
+               which_type == TxoutType::MULTISIG);
+    }
+    if (which_type == TxoutType::NONSTANDARD) {
+        assert(!is_standard_ret);
+    }
     if (which_type == TxoutType::NULL_DATA) {
         assert(script.IsUnspendable());
     }