[MongoDB Replication] Raw Change Streams (#591)

* Add rawChangeStream implementation.

* Use the new rawChangeStream().

* Remove old openChangeStream.

* Use raw responses.

* Defer parsing change stream documents.

* Redo replication metrics.

* Cleanup.

* Fix collection-level testing.

* Add retries for rawChangeStream.

* Re-use session for retries.

* Fix killCursors.

* Handle startAfter.

* Improve abort handling; add comments.

* Add tests for resuming streams.

* Improve and test abort handling.

* Rename test.

* Add test for replicating from multiple databases in the same cluster.

* Changeset.

* Fix `batchesSeen`.

* Rename options.

Author: rkistner

.changeset/chilled-bags-complain.md

@@ -0,0 +1,5 @@
+---
+'@powersync/service-module-mongodb': minor
+---
+
+Use custom MongoDB change stream implementation to get better low-level control.