WIP Use ContactResolver for eventReceivedSlot
WIP Debug and timing for contact stuff
Add contact cache and pending list to ContactResolver
Remove contactCache from EventModelPrivate
WIP Disable contactCache use in RecentContactsModel, needs refactor
Set up contact listening on setResolveContacts

Before, this was inconsistently enabled after the query was executed, in
a very bug-prone way. It's cheap to enable on an empty model.