Enable tests to store additional metadata for waiving as logs

[comps]

When the hardening/scanning tests parse oscap xccdf eval outputs (stdout/err, or via results ARF XML as suggested by #24), they could collect additional metadata - ie. openscap probe details about file paths that failed the check, or other details.

Since TMT doesn't allow arbitrary result line extensions, these would have to be stored as logs (for each reported rule result), because adding them to reported name would likely be too verbose.

They could then also be accessible to waiving logic as a dict() of logs, so a waiving rule could match on oscap probe details, ie.

    rhel == 8 and '/etc/passwd' in logs['paths']

or something of that nature.