[FLINK-19659][table-planner] Array type supports equals and not_equal…

[wangxlong]

…s operator when element types are different but castable

What is the purpose of the change

Array type supports equals and not_equals operator when element types are different but castable

Brief change log

Add the cast code between array and array

Verifying this change

This change added tests and can be verified as follows:

1. Add test to ScalarOperatorsTest#testCompareOperator to verify the comparison between array and array
2. Add test to ScalarOperatorsTest#testCast to verify that it is castable between array and array

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 / don't know)
• The runtime per-record code paths (performance sensitive): (no / don't know)
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn/Mesos, ZooKeeper: (no / don't know)
• The S3 file system connector: (no / don't know)

Documentation

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

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Last check on commit b4a79b0 (Tue Dec 08 07:38:24 UTC 2020)

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[twalthr]

Thanks @wangxlong. I will do a full review soon. Could you use the new test base?
org.apache.flink.table.planner.functions.CastFunctionITCase

It was recently added for casting rows to rows. It will be further extended as part of FLINK-17321.

[wangxlong]

Thanks @twalthr. Yes, I will update it soon.

[wangxlong]

It is ready to be reviewed. Thanks for having a look in your free time. @twalthr