When sqlite encounters certain "critical errors" during a transaction (like when the db exceeds available storage), it may automatically roll back the transaction. We already have code that attempts to handle rollbacks due to critical errors, but it interacts poorly with the savepoint-based explicit transactions set up by .transaction() and .transactionSync(), triggering "no such savepoint" internal errors when it attempts to commit or roll back a savepoint that had already been removed. This PR updates the handling to suppress failures due to missing savepoints after critical errors.

It also addresses an edge case where a critical error during an explicit .transaction() did not propagate a broken exception to the caller.