[FLINK-26119][connectors/common] AsyncSinkWriterStateSerializer to @PublicEvolving

[dannycranmer]

What is the purpose of the change

AsyncSinkWriterStateSerializer is annotated @Internal, however downstream modules need to extend this class. Therefore it should be marked @PublicEvolving.

Brief change log

• AsyncSinkWriterStateSerializer swtiched from @Internal to @PublicEvolving

Verifying this change

This change is a trivial rework / code cleanup without any test coverage.

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
• If yes, how is the feature documented? n/a

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Automated Checks

Last check on commit 1294b28 (Tue Feb 15 08:33:46 UTC 2022)

Warnings:

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

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Review Progress

• ❓ 1. The [description] looks good.
• ❓ 2. There is [consensus] that the contribution should go into to Flink.
• ❓ 3. Needs [attention] from.
• ❓ 4. The change fits into the overall [architecture].
• ❓ 5. Overall code [quality] is good.

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CI report:

• 7df95ee Azure: FAILURE
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[fapaul]

LGTM I ran the ArchitectureTest locally and everything passed.

[dannycranmer]

ArchitectureTest passes on CI.