This PR makes it so the Consul sync logic will ignore operations that
do not specify an action to take (i.e. [de-]register [services|checks]).
Ideally such noops would be discarded at the callsites (i.e. users
of [Create|Update|Remove]Workload], but we can also be defensive
at the commit point.
Also adds 2 trace logging statements which are helpful for diagnosing
sync operations with Consul - when they happen and why.
Fixes#10797
