[FLINK-32249][table-planner] Use proper toString conversion when constructing column comments for CatalogTable

[lincoln-lil]

What is the purpose of the change

The current SqlCreateTableConverter does not use the correct toString method when constructing column comments for CatalogTable, which may cause sql-client users and catalog implementers to encounter problems with Chinese characters in column comments not being displayed as expected.

Brief change log

update the toString logic for column comments in SqlCreateTableConverter

Verifying this change

Add Chinese characters in test cases of SqlDdlToOperationConverterTest

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)

[flinkbot]

CI report:

• a83819b Azure: SUCCESS

Bot commands

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• @flinkbot run azure re-run the last Azure build

[Aitozi]

LGTM

[libenchao]

+1