unit: swift unit tests for replication events (#2485)
unit: swift unit tests for replication events (#2485)

* validated whether there is only single events are fired when document replication custom conflict resolution happens, and when CCR exception is thrown(skips the ccr).
couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios