prometheus: Add missing operator to metric_family_iterator
prometheus: Add missing operator to metric_family_iterator

This adds the equal (==) and postfix++ operator to the
metric_family_iterator.

Signed-off-by: Amnon Heiman <ed5fc74c4692051ad0b19749fd7cea6ec2d74b9e@scylladb.com>

scylladb/seastar,avikivity/seastar,dreamsxin/seastar,cloudius-systems/seastar,scylladb/seastar,avikivity/seastar,syuu1228/seastar,cloudius-systems/seastar,syuu1228/seastar,dreamsxin/seastar,scylladb/seastar,avikivity/seastar,dreamsxin/seastar,syuu1228/seastar,cloudius-systems/seastar