[FLINK-23583][table-common] Introduce SubRowData

[Airblader]

What is the purpose of the change

This introduced SubRowData, a counterpart to JoinedRowData, which allows reducing a RowData to a subset. The need for this arises naturally e.g. when implementing sink connectors with a format and metadata as the sink receives a row with appended metadata, but needs to serialize only the part without the metadata

Verifying this change

This change added tests and can be verified as follows:

• SubRowDataTest

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): yes
• 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? yes
• If yes, how is the feature documented? JavaDocs

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Automated Checks

Last check on commit 8d7493f (Mon Aug 02 10:21:16 UTC 2021)

Warnings:

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