Support zstd compressed MDF reading in old-style IO

A crude proof of concept for guiding the discussion in https://gitlab.cern.ch/lhcb/opg/-/issues/41. It seems to work for all of the offline use cases that we actually have at the moment.

See https://gitlab.cern.ch/lhcb/opg/-/issues/41 for the motivation for this MR. This MR is ready and tested.

cc @sponce @clemenci @bcouturi

Note that is now part of !2993 (merged), so it should not be merged unless !2993 (merged) does not make it to production