Correct and tune equinox-sync template progress management

[bartelink]

The current equinox-sync impl does not deal with the following correctly:

• if 5 retries fails to save the changes for a batch, it gives up, and CFP cannot be convinced not to write progress in this instance
• there are bugs in the result processing which cause some items not to be processed
• logging is extremely noisy compared to sister PR for EventStore

This PR brings over work done in the context of the ingester template in (#16) so will appear slightly overkill...

• Target Equinox 2.0.0-preview5 in order to avail of manual checkpointing and logging
• Make all progress writing subject to stream validations from CosmosIngester
• Make progress writing async and lazy
• Allow loading to run in advance of stream syncing
• Add Seq logging support