Refactor tests for startBatch() -> createWriter()

[rkistner]

This ports a refactoring from #468:

1. Replace startBatch() using a callback with createWriter() as an AsyncDisposable.
2. Pull that refactoring throughout the tests.
3. In tests, replace a hardcoded TEST_TABLE with await resolveTestTable(writer), which will eventually return a real SourceTable instead of a mocked one.
4. There are also other minor test changes to align the tests more with [Incremental Reprocessing] [WIP] Proof-of-concept incremental reprocessing for MongoDB #468.

This does not remove the internal usage of startBatch() yet - it mostly focuses on the test refactor. The internal usage of startBatch() can be tackled next.

The main goal is to reduce the diff size and potential for merge conflicts from #468.

[changeset-bot]

🦋 Changeset detected

Latest commit: 54ceed8

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 12 packages

Name	Type
@powersync/service-module-postgres-storage	Patch
@powersync/service-module-mongodb-storage	Patch
@powersync/service-core-tests	Patch
@powersync/service-module-mongodb	Patch
@powersync/service-core	Patch
@powersync/service-schema	Patch
@powersync/service-module-mssql	Patch
@powersync/service-module-mysql	Patch
@powersync/service-module-postgres	Patch
@powersync/service-image	Patch
@powersync/service-module-core	Patch
test-client	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR