Fix upload queue monitoring issues

[rkistner]

The is a combination of multiple related issues:

1. To detect whether we should trigger a crud upload iteration, the entire database was watched, instead of only the ps_crud table.
2. Update notifications were not throttled at all on web, and not correctly handled during transactions (see Debounce update notifications sqlite_async.dart#68 for the issue and fix).
3. The connection status was changed to uploading: true whenever we get an update notification, rather than only when there is something to upload.

The result was that on Flutter web, after an initial sync of 10k+ rows, there would be a couple of seconds of the sync indicator flickering between "uploading" and "connected". This also added performance overhead.

TODO:

• Include sqlite_async dependency updates for Debounce update notifications sqlite_async.dart#68 when released.
• Rebase onto main branch.

[mugikhan]

LGTM.