In 5.0 we added a timestamp to each database version so the _uuidDisambiguatingSequenceNum can be now removed. In fact it was used to make UUID comparable locally on every shard, now we can simply use the timestamp associated to the database in order to understand which is the newer one.

As part of this ticket we should:

• Remove the ComparableDatabaseVersion::_uuidDisambiguatingSequenceNum class property
• Implement comparison operators for DatabaseVersion class based on timestamp.
• Replace usages of ComparableDatabaseVersion outside of the CatalogCache with the new DatabaseVersion comparision operator.
• Move the ComparableDatabaseVersion class inside the catalog cache since it will be the only place in which we will needed (for forcing catalog cache incremental refreshes).