In prod there is a stream processor with timeseries $emit hitting errors like: bulk_write_exception::raw_server_error() contains unexpected (0) number of write error.

This PR adds some logs so we can see what the original mongocxx error was:

https://github.com/10gen/mongo/pull/20051

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There might be a bug in our code we need to fix in merge_operator and timeseries_emit_operator.