[Fix] CRUD Upload on Reconnect

[stevensJourney]

Overview

This fixes an issue where CRUD uploads are not triggered when the SDK reconnects to the PowerSync service after being offline.

Previously uploads were only triggered when an initial call to .connect has been made or when changes to the ps_crud table have occurred. If an application called .connect successfully, then went offline and made CRUD operations - the SDK would not trigger a CRUD upload once it had re-established a connection.

This now triggers a CRUD upload whenever the SDK establishes a connection or a change has been made to ps_crud.

Testing

This was tested locally and unit tests have been added using a mock PowerSync service.

[mugikhan]

LGTM!

[stevensJourney]

Some unit tests are broken. Will investigate.

[rkistner]

For my own reference, since I was confused with how this could happen:

1. If a crud uploads fails with just an upload error, it is automatically retried indefinitely.
2. If the user explicitly disconnects and reconnects, the crud loop is restarted, and should try again.
3. If however a crud upload fails and isConnected == false, then the current crud iteration stops, and waits for more changes. This prevents continuous retrying of uploads while the user is offline.

The fix here targets (3), by basically triggering the "there are more changes" stream when the sync connection is established again.

[lucastex]

@stevensJourney thanks for being working on this. We're following the PR because it got a huge impact in our last update here. Thanks.

[stevensJourney]

Some unit tests are broken. Will investigate.

Tests pass more consistently now. The main issues were from the full powersync reconnect test timing out: this test calls the SDK close method which performs a disconnect and closes the SQLite DB. A race condition caused the SQLite DB to close before the CRUD loop exited. This caused an exception to be thrown when the CRUD loop checked for CRUD operations - the caught exception added a retry delay which kept the sync isolate alive for an additional 5 seconds.

I've shuffled around the CRUD loop exit checks in order to exit the loop faster when disconnecting or closing.