improve errors logs in direct messages

[Khady]

Currently the error logs sent next to the error notifications in direct messages are 200 lines long. We could make the experience more comfortable for common cases

• send a code block with only the last 30 lines and make the text attachment longer. The idea is to avoid a click for simple errors, no need to "click to expand" and also shows more info by default on mobile
• extract errors directly from the logs. For this one, ideally we would like dune to be able to output logs in a format such as sexp or json which can be easily worked with by a machine (should open an issue upstream to request this feature). But living in a non ideal world, one first solution might be to use regexp. Some inspiration
  • the old regexp from tuareg https://github.com/Chris00/tuareg/blob/de3777d47b4d7e7b11990d505c5e07cf8f3a67aa/tuareg.el#L2647-L2653
  • and the modern rx version https://github.com/Chris00/tuareg/blob/53ce2fdfdd372d52f3a6547c33b687e7d403357a/tuareg.el#L3334-L3381 (I'm not sure which is more correct, it changed a few times in between)
  • from ocaml-setup Add the OCaml problem matcher ocaml/setup-ocaml#695
  • from vscode https://github.com/ocamllabs/vscode-ocaml-platform/blob/b8a7ffc190b091d72f0326ccd753fcf80de2e103/package.json#L1246-L1261