unit: add basic unit tests for custom conflict - objc (#2441)
unit: add basic unit tests for custom conflict - objc (#2441)

* test conflict handler with remote win, local win, delete local , delete remote
* name the tests and made consistent with document
* kept the resolver as constructor.
couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios