Monitor bad AcceptBlock calls

E.g. 
```
2023-05-08T15:36:48Z ERROR: AcceptBlock: bad-witness-nonce-size, ContextualCheckBlock : invalid witness reserved value size
2023-05-08T15:36:48Z ERROR: ProcessNewBlock: AcceptBlock FAILED (bad-witness-nonce-size, ContextualCheckBlock : invalid witness reserved value size)
```

(from https://0bin.net/paste/ErHctHfs#yHXnmymeDKmBdLpqr7IYFZsV3IoX4vrV0UNiLQAB+Tu, IRC logs 2023-05-08)