As part of changing the CollectionIndexes to use the UUID instead of the CollectionGeneration, we will need to update the ComparableIndexVersion.

As part of this ticket we need to:

• Make the comparableIndexVersion contain only the index timestamp and a forced refresh sequence number
• Change the comparison of ComparableIndexVersions so that all boost::none index versions compare as the same
• Ensure that any transition from boost::none -> valid timestamp or timestamp -> boost::none triggers a refresh
• Modify the index cache to make the GlobalIndexesCache optional --> we should not get a GlobalIndexesCache object from the cache if the time in store is boost::none