Comply with legacy sync protocol
Comply with legacy sync protocol

In core-5 based sync, the protocol does not support ArrayInsert with a
value. Therefore we need to split th eoperation into an ArrayInsert with
null value followed by an ArraySet with the value.

realm/realm-core,realm/realm-core,realm/realm-core,realm/realm-core,realm/realm-core,realm/realm-core,realm/realm-core