perf: Improve performance of the apply changes method by grouping rows.

[bvanelli]

Improves the speed when having thousands of entries on the sync backlog by grouping them together. This should make sure that the inserts are done in a single query (INSERT ... ON CONFLICT UPDATE), but should also newly created entities fields together, making the queries more efficient. Over testing, this helped improve performance of budget with high number of entries high, but also keep the performance of newly created budgets (without many changes) the same.

Closes #87

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.67%. Comparing base (0e391ee) to head (13f4dad).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #88   +/-   ##
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  Coverage   97.66%   97.67%           
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  Files          16       16           
  Lines        2188     2194    +6     
=======================================
+ Hits         2137     2143    +6     
  Misses         51       51           

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