[Bugfix][Kafka] In kafka flow mode, stop offse should be Long.MAX_VALUE

[Carl-Zhou-CN]

Purpose of this pull request

Does this PR introduce any user-facing change?

How was this patch tested?

Current test

Check list

• If any new Jar binary package adding in your PR, please add License Notice according
  New License Guide
• If necessary, please update the documentation to describe the new feature. https://github.com/apache/seatunnel/tree/dev/docs
• If you are contributing the connector code, please check that the following files are updated:
  1. Update plugin-mapping.properties and add new connector information in it
  2. Update the pom file of seatunnel-dist
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  4. Add e2e testcase in seatunnel-e2e
  5. Update connector plugin_config
• Update the release-note.

[hailin0]

Please add test cases

[weipengfei-sj]

When running tasks in a flow mode, an empty map array is returned, and a NullPointerException will occur at this location.

It also needs to be adjusted to the following format.
split.setEndOffset(
latestOffsets.getOrDefault(
split.getTopicPartition(), Long.MAX_VALUE));