Limit producer batch messages by size in bytes as well

[AfonsoRibeiro]

To prevent the producer from sending batches that are bigger than allowed by the pulsar server, a limit in bytes should be possible to configure. Or at least a soft threshold that when reached sends the batch (much easier to implement and it appears it is also done in the go client).

[tisonkun]

This is partially resolved by https://github.com/streamnative/pulsar-rs/pull/269.

Keep open for a while since there are still several potential improvements can be made. See https://github.com/streamnative/pulsar-rs/pull/269#pullrequestreview-1382771811.

[fatelei]

i want to try this issue