We try to identify relay error messages by parsing the response and rougly matching string conents. When error can't be identified builder emits a warn log.

See `SubmitBlockErr` enum for context.

There are new non-ctitical relay errors that we need to handle

This is the summary of err field of log with the message "Error submitting block to the relay"

```
Relay error: Relay error: Relay error: (code: 400, message: already using a newer payload)
Relay error: Internal Error
Relay error: Unknown relay response, status: 202 Accepted, body: "accepted bid below floor, skipped validation"
Relay error: Unknown relay response, status: 413 Payload Too Large, body: 413 Request Entity Too Large

413 Request Entity Too Large

---

nginx
Relay error: Unknown relay response, status: 520 , body: error code: 520
Relay error: Unknown relay response, status: 502 Bad Gateway, body: 502 Bad Gateway

502 Bad Gateway

---

nginx
Relay error: Unknown relay response, status: 502 Bad Gateway, body: error code: 502
```