[validation] Make script error messages uniform for parallel/single validation

This makes the debug output mostly the same for -par=1 and parallel validation runs. Of course,
parallel validation is non-deterministic in what error it may encounter first if there are
multiple issues. Also, the way certain script-related and non-script-related checks are
performed differs between the two modes still, which may result in discrepancies.

test/functional/feature_taproot.py

@@ -1285,7 +1285,6 @@ class TaprootTest(BitcoinTestFramework):
     def set_test_params(self):
         self.num_nodes = 1
         self.setup_clean_chain = True
-        self.extra_args = [["-par=1"]]
 
     def block_submit(self, node, txs, msg, err_msg, cb_pubkey=None, fees=0, sigops_weight=0, witness=False, accept=False):