[FLINK-21172][canal][json] canal-json format include es field

[SteNicholas]

What is the purpose of the change

Metadata column of CanalJsonDecodingFormat doesn't support to extract the es field of Canal JSON record, which field extracts from MySQL binlog represent for the row data real change time in MySQL. The event-timestamp metadata column expresses the event time.

Brief change log

• CanalJsonDecodingFormat adds event-timestamp metadata column for the es field of Canal JSON record.

Verifying this change

• CanalJsonSerDeSchemaTest adds the validation to verify whether the event-timestamp metadata column value is equal to the value of es field.
• KafkaChangelogTableITCase adds the event-timestamp metadata column in the DDL of Kafka source table to verify the event-timestamp metadata column could be used as event time.

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

• Dependencies (does it add or upgrade a dependency): (yes / no)
• The public API, i.e., is any changed class annotated with @Public(Evolving): (yes / no)
• The serializers: (yes / no / don't know)
• The runtime per-record code paths (performance sensitive): (yes / no / don't know)
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn/Mesos, ZooKeeper: (yes / no / don't know)
• The S3 file system connector: (yes / no / don't know)

Documentation

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

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Last check on commit c7bea18 (Fri May 28 08:15:53 UTC 2021)

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[SteNicholas]

@wuchong , the CI result is successful. If you are available, please help to review this pull request.

[wuchong]

Thanks @SteNicholas . I only left a single minor comment.

[wuchong]

LGTM.