feat: Statistics.to_json

[tiferrei]

This PR adds a to_json method for Statistics.t.

Note: This method uses Yojson.Basic.t for consistency with the rest of the repo. In the future it is probably best to convert the usages to Yojson.Safe.t.

[filipeom]

Thanks! Looks like the colibri2 CI is broken because https://git.frama-c.com/pub/ is acting up again 😢

[tiferrei]

Yes I had to remove those repos locally. I think the links are dead :(

[hra687261]

Not permanently dead (I hope), it seems to be some kind of ddos because every once in a while it works ...
The Colibri2 CI should probably be disabled for the meantime, until that gets fixed at some point ...

[filipeom]

Not permanently dead (I hope), it seems to be some kind of ddos because every once in a while it works ...

Yeah, it does seem a bit intermittent. I changed the opam-repositories fields in CI to use https://opam.ocaml.org which fixed the failures to fetch packages from the frama-c gitlab. Unfortunately, since colibri2 is pinned it will fail to clone the repo and fail because it will use the latest colibri2 pacakge in opam-repo 😢

The Colibri2 CI should probably be disabled for the meantime, until that gets fixed at some point ...

I'll leave it on for now since it is not required to merge PRs. Hopefully it will be fixed soon

[filipeom]

Thanks again! I'll open a issue to reminds us to change to Yojson.Safe.t 😄