v1.9.1-beta01: Fix synchronizer stop, scan loop, and SQLite isolation

- Fix SdkSynchronizer.stop() race condition: use synchronous scope.cancel()
  instead of async self-cancellation that never completed
- Fix scan loop: scan once after all downloads complete instead of per-batch
- Use fresh SQLiteDatabase connection for getLastScannedHeight() to avoid
  reading stale Room-cached values
- Bump version to 1.9.1-beta01
- Update Cargo dependencies

darkside-test-lib/src/androidTest/java/cash/z/ecc/android/sdk/darkside/test/DarksideTestCoordinator.kt

@@ -101,13 +101,13 @@ class DarksideTestCoordinator(val wallet: TestWallet) {
                 twig("got processor status $it")
                 if (it == Synchronizer.Status.DISCONNECTED) {
                     twig("waiting a bit before giving up on connection...")
-                } else if (targetHeight != null && (synchronizer as SdkSynchronizer).processor.getLastScannedHeight() < targetHeight) {
+                } else if (targetHeight != null && ((synchronizer as SdkSynchronizer).processor.getLastScannedHeight() ?: synchronizer.network.saplingActivationHeight) < targetHeight) {
                     twig("awaiting new blocks from server...")
                 }
             }.map {
                 // whenever we're waiting for a target height, for simplicity, if we're sleeping,
                 // and in between polls, then consider it that we're not synced
-                if (targetHeight != null && (synchronizer as SdkSynchronizer).processor.getLastScannedHeight() < targetHeight) {
+                if (targetHeight != null && ((synchronizer as SdkSynchronizer).processor.getLastScannedHeight() ?: synchronizer.network.saplingActivationHeight) < targetHeight) {
                     twig("switching status to DOWNLOADING because we're still waiting for height $targetHeight")
                     Synchronizer.Status.DOWNLOADING
                 } else {