truncation support

[kortemik]

Description
currently rlp_03 accepts records of any size, however there may be cases where limiting the maximum payload size is preferred. These may be such as clients sending accidentally (or deliberately) large relp frames and these reserve quite much memory on the processing side.

Use case or motivation behind the feature request
Support configurable limit for payload truncation. RelpParser would store up-to-the-limit amount of data and then process the rest but not store. Truncated frames should be marked as such and the total size before truncation should be made available.

Related issues

Additional context