[FEATURE] : Optimize syncExpenses mutation

[alinauroz]

Describe the feature
The synchronization of expenses with OpenCollective encounters difficulties when dealing with rounds containing several hundred expenses. This is primarily due to Vercel's termination of the sync function after one minute, which falls short of the time required for the synchronization process.

The proposed solution involves optimizing the process by exclusively updating modified data, employing raw SQL queries, and retrieving solely the necessary data from database.