[FLINK-32721] [planner] Support CharType for the MaxAggFunction

[liuyongvs]

What is the purpose of the change

Support CharType for the MaxAggFunction.*

Brief change log

• Support CharType for the MaxAggFunction like MinAggFunction*

Verifying this change

• original unit test *

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:

• ffc32e9 Azure: SUCCESS

Bot commands

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

[lsyldliu]

@liuyongvs Thanks for your contribution, this will be fixed by #18375, this pr will be closed later.

[liuyongvs]

@liuyongvs Thanks for your contribution, this will be fixed by #18375, this pr will be closed later.

@lsyldliu thanks for your clarify, i also add comments for the pr you refer

[liuyongvs]

i close it now @lsyldliu @xuyangzhong