Child of CBLReadOnly{Array/Dict} should also be read-only
Child of CBLReadOnly{Array/Dict} should also be read-only

Check the parent collection's mutableChildren property to decide which
class to instantiate.

couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,amco/couchbase-lite-ios,couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,amco/couchbase-lite-ios,amco/couchbase-lite-ios,amco/couchbase-lite-ios,amco/couchbase-lite-ios,amco/couchbase-lite-ios,amco/couchbase-lite-ios