replicators: Add controller_channel logic for resnapshot tables

[altmannmarcelo]

Add controller_channel logic for resnapshot tables. This handles the replicator receiver side of the message by dropping the required table from readyset and then informing the main loop via ReadySetError::ResnapshotNeeded error that a resnapshot is required. When the database adaptor starts once again, it will notice the missing table and resnapshot it.

Note: The message sender is not yet implemented and will be implemented on a separate commit.