Allocator's metrics for filter counts should include framework id.

MESOS-4722 added per-role filter metrics, which isn't very helpful for figuring out which framework is filtering offers when frameworks are sharing a role:

"allocator/mesos/offer_filters/roles/*/active": 88,
"allocator/mesos/offer_filters/roles/monitoring-role/active": 0,
"allocator/mesos/offer_filters/roles/slave_public/active": 171,
"allocator/mesos/offer_filters/roles/spark-dispatcher/active": 288,

If there are multiple frameworks sharing these roles, it becomes hard to diagnose what's happening.

*Also, note that hierarchical roles here are exposing their slashes directly, which makes parsing more difficult.* We should consider encoding the role, much like we did with the framework names, see MESOS-7055 and https://github.com/apache/mesos/commit/45fa0593790632a5c1231b350921281dded1c1aa#diff-544616f159a85e652cd4744ef4729921R561

We could consider "breaking" backwards compatibility here as I doubt many users are relying on these metric names, and we could send an email to the user list soliciting any objections before doing so.