integrate opam lint information into obi index

[avsm]

The lints branch of obi-logs contains opam-lint that is regularly run the main opam repository.

There is information in there relevant to package maintainers, such as broken distfiles and/or constraint inconsistencies. We should hook this into the main Obi index by parsing the output.

Fixing this is blocked on ocaml/opam#3342 in upstream opam, since the existing opam lint output is difficult to parse directly. (cc @AltGr as fyi)