OptionStrList takes a filename as its value. It reads the file into a
list of strings in the protobuf. On the server side, the values are
unpacked and made available as std::vector<std::string>.

For example implementation, see "cta-admin repack add"

The jobs will now remain attached to the agent of the drive process. The garbage collector
process will now requeue them instead of drive process. This will allow the drive process
to restart faster for a new session and the drive process to requeue the jobs faster a it
processes jobs in bulk.

We should not be overdoing it: it should be owned by user cta but we do not care about the group. This was failing in CI as cta group does not exist anymore

Also cut the main garbage collection function into smaller bits.
We requeue jobs in batches of 500.

Successful retrieve requests are asynchronously deleted as soon as they
are complete. Then from time to time (every 500), the requests get removed from
process ownership in bulk.

Retry once the archiveretrieve CI job, as sometimes the eos instance reports no space for a possible bad timing between the FST and the MGM.