Add a way to view current offer filters

Looking at just mesos, it's currently not possible to see which offer filters are active for which amount of time.

The closest one can get is to check whether a filter currently exists, either by looking at via the `metrics/snapshot` if per-frameworks metrics are enabled or by scanning the master logs for this message

      VLOG(1) << "Filtered offer with " << resources
              << " on agent " << slaveId
              << " for role " << role
              << " of framework " << frameworkId;

However, that does not tell the user how long the filter was there, which resources it contains and how long it will stay.

Maybe MESOS-8621 would be a viable way to surface this information.