[FLINK-23953] In the AvroSerializerSnapshot set the serializer compatibility to 'AS IS' in case when underlying Avro schemas are compatible

[izeigerman]

What is the purpose of the change

To fix schema evolution for Avro records by eliminating the state migration in the scenario when the old and the new Avro schemas are compatible.

Brief change log

• Resolve the schema compatibility status to "AS IS" in case when the old and the new Avro schemas are compatible.

Verifying this change

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: yes
• The runtime per-record code paths (performance sensitive): no
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: yes
• The S3 file system connector: no

Documentation

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

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Automated Checks

Last check on commit abc6c4d (Wed Aug 25 00:13:15 UTC 2021)

Warnings:

• No documentation files were touched! Remember to keep the Flink docs up to date!
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CI report:

• d883bc2 Azure: SUCCESS

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[masteryhx]

@izeigerman Hi, Are you still working on this ? Would you mind rebasing the new master ?