Add byte size limit for append request

Why it matters

This feature introduces a limit on the total byte size of append request batches in Keeper to prevent excessively large batches that could impact system stability and performance. It helps ensure better resource management and consistent coordination behavior in distributed setups.

How to use it

Set the limit using the keeper_server.coordination_settings.max_requests_append_bytes_size configuration parameter to control the maximum allowed batch size of append requests in bytes.