Enable message offset auto commit in pulsar client consumer

**Is your feature request related to a problem? Please describe.**
When consume from a pulsar topic, it need to commit the consumed message offset in the program code by use pulsar client `acknowledge` method, this problem also appear in pulsar-flink-connector, which need commit the offset by flink checkpoint. it may be better to auto commit the offset like kafka client.

**Describe the solution you'd like**
start a timer thread in pulsar client, and auto commit the pulsar topic offset by a fixed interval.

**Describe alternatives you've considered**

**Additional context**

Start by reading the Pulsar client consumer acknowledgement flow and its existing consumer configuration; the issue names no files or tests. Clarify the auto-commit API, interval semantics, lifecycle, and interaction with Flink checkpoints, then add coverage showing offsets are committed at the configured interval.

Written by the indexing model from the issue text.