[FLINK-38432][python] Fix missing finish/reset for keyWriter/valueWriter in ArrowMapWriter

[wzx140]

What is the purpose of the change

The finish and reset methods in org.apache.flink.table.runtime.arrow.writers.MapWriter should be implemented in the same way as in org.apache.flink.table.runtime.arrow.writers.RowWriter.

Otherwise, the following sequence will lead to incorrect behavior:

MapWriter.write
// Arrow data is right
MapWriter.finish
MapWriter.reset
MapWriter.write
// Arrow data is wrong, map is null
MapWriter.finish

Brief change log

Add finish/reset for keyWriter/valueWriter in ArrowMapWriter.

Verifying this change

Add UT

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): (no)
• The public API, i.e., is any changed class annotated with @Public(Evolving): (no)
• The serializers: (no)
• The runtime per-record code paths (performance sensitive): (no)
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: (no)
• The S3 file system connector: (no)

Documentation

• Does this pull request introduce a new feature? (no)
• If yes, how is the feature documented? (not documented)

[flinkbot]

CI report:

• 6a76bda Azure: SUCCESS

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