Move the `waitForSynced` method from `frontend` to `nbstore worker` to make the wait more reliable
<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## Summary by CodeRabbit
- **New Features**
- Added explicit tracking of document updating state to indicate when data is being applied or saved.
- Introduced new methods to wait for update and synchronization completion with abort support.
- **Improvements**
- Applied throttling with leading and trailing emissions to state observables for smoother UI updates.
- Refined synchronization waiting logic for clearer separation between update completion and sync completion.
- Removed throttling in workspace selector component for more immediate state feedback.
- Updated import and clipper services to use the new synchronization waiting methods.
- Simplified asynchronous waiting logic in indexer synchronization methods.
- **Bug Fixes**
- Enhanced accuracy and reliability of document update and sync status indicators.
- **Tests**
- Increased wait timeout in avatar selection test to improve stability.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
EYHN