Add constant scriptCode policy in non-segwit scripts

This disables OP_CODESEPARATOR in non-segwit scripts (even in an unexecuted branch), and makes a positive FindAndDelete result invalid. This ensures that the scriptCode serialized in SignatureHash() is always the same as the script passing to the EvalScript.

src/test/script_tests.cpp

@@ -97,6 +97,8 @@ static ScriptErrorDesc script_errors[]={
     {SCRIPT_ERR_WITNESS_MALLEATED_P2SH, "WITNESS_MALLEATED_P2SH"},
     {SCRIPT_ERR_WITNESS_UNEXPECTED, "WITNESS_UNEXPECTED"},
     {SCRIPT_ERR_WITNESS_PUBKEYTYPE, "WITNESS_PUBKEYTYPE"},
+    {SCRIPT_ERR_OP_CODESEPARATOR, "OP_CODESEPARATOR"},
+    {SCRIPT_ERR_SIG_FINDANDDELETE, "SIG_FINDANDDELETE"},
 };
 
 const char *FormatScriptError(ScriptError_t err)