New syncing strategy to improve local-first mode synchronization time.

[JC-comp]

@abraunegg
Regarding the handling of remote first and local first mode, the current solution is

• In Remote first mode: attempting to download everything and upload only new local items
• In local first mode: attempting to upload everything locally and download only new items from OneDrive

All the actions to take can be like summarized in the following table.
If this is the case, the sequence of executing fetchOneDriveDeltaAPIResponse, scanLocalFilesystemPathForNewData, and performDatabaseConsistencyAndIntegrityCheck doesn't matter. By following the rules outlined in the table below, all items can eventually achieve the correct sync state.

But executing fetchOneDriveDeltaAPIResponse first can significantly reduce the synchronization time. By retrieving 200+ items from OneDrive in a single delta request and syncing them, the synchronized items in the database can then be leveraged by the other two functions to minimize requests to OneDrive for obtaining online state, thus reducing overall processing time.

For example, if we perform scanLocalFilesystemPathForNewData first in the current local-first mode, rule 5 dictates that the DB entry does not exist, requiring single requests for each item to bring it into sync. However, if we execute fetchOneDriveDeltaAPIResponse first, we can synchronize 200+ items at once and store them in the database. This converts the original check of rule 5 into rule 1 or 2, both of which don't require action. All rules from 2 to 10 can be consolidated into rule 0 or 1, which don't require any operation after fetchOneDriveDeltaAPIResponse and querying local items is fast and inexpensive. Only rule 11, which involves scanning for new local files to upload, requires additional requests to OneDrive.

By implementing this strategy, it can significantly reduce syncing time for the local-first mode, especially for users with large number of files. Do you think this idea is feasible?

Rrule	Exists ( Remote / Local )	InSync ( Remote / Local )	InDB	Action
0	❌/❌	-	-	Nothing
1	✔/✔	✔/✔	✔	Nothing
2	✔/✔	❌/✔	✔	Download
3	✔/✔	✔/❌	✔	Upload
4	✔/✔	❌/❌	✔	Remote first: Download Local first: Upload
5	✔/✔	-	❌	Remote first: Download Local first: Upload
6	✔/❌	✔/-	✔	Delete
7	✔/❌	❌/-	✔	Remote first: Download Local first: Delete
8	✔/❌	-	❌	Download
9	❌/✔	-/✔	✔	Delete
10	❌/✔	-/❌	✔	Remote first: Delete Local first: Upload
11	❌/✔	-	❌	Upload

'-' means don't care