opam-2.0 workflows may timeout or fail with a cyclic dependency error

[jmid]

This is known issue that will go away once we retire the opam-2.0 workflows. I'm opening it in the interest of knowledge sharing, so that outside contributors have a chance of learning.

Old version of opam had a weaker solver that started falling once constraints became too many/complicated for it. The old opam2 check was added there mostly to ensure that we are not regressing, it is probably time to start discussing if it is still needed

Originally posted by @mseri in https://github.com/ocaml/opam-repository/issues/28910#issuecomment-3567798259