chore(engine): increase job/incident exception message cutoff

- raises cutoff from 255 to 666 characters
- reasoning: 4000 byte are the hard size limitiations of a message on
  Oracle and DB2. However, we cannot make assumptions about the database's
  character set. On Oracle, we use Unicode-encoded fields. A Unicode
  supplementary character can take up to 6 byte on Oracle. 6 * 666 = 3996.
  On DB2, we cannot make any assumption about the database charset but
  6 bytes per character appear to be a conservative value
- makes exception message cutoff configurable by exposing the constant
  field

related to CAM-2819