feat(mon-pages): filter services by their labels

The same two conditions on the service side, over the service's own
labels, tags, contacts and contact groups rather than the host's.

The models carry the "Service" prefix the rest of the module already
uses, since the OpenAPI spec registers component schemas by class name
across every endpoint family and an unprefixed name would collide with
the identically shaped hosts one.

CMK-38149

Change-Id: Ifc96d9bf1a97b9d92bc8c34e1ee57ede67bd491c