[FLINK-34978][State] Introduce Asynchronous State APIs

[Zakelly]

What is the purpose of the change

As discussed in FLIP-424, we will introduce a new set of State APIs for asynchronous state access. This PR provides the definition of this API as described in FLIP-424.

Brief change log

• New api under org.apache.flink.api.common.state.v2.

Verifying this change

This change is a trivial rework 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? yes
• If yes, how is the feature documented? not documented

[flinkbot]

CI report:

• 0aac348 Azure: SUCCESS

Bot commands

The @flinkbot bot supports the following commands:

• @flinkbot run azure re-run the last Azure build

[Zakelly]

Rebase on FLINK-34548 and introduce this in flink-core-api

[masteryhx]

Thanks for the PR.
PTAL my comments.

[Zakelly]

@masteryhx Thanks for your suggestion! I modified accordingly, PTAL. Thanks!

By the way, the CI failure is caused by #24596

[masteryhx]

@masteryhx Thanks for your suggestion! I modified accordingly, PTAL. Thanks!

By the way, the CI failure is caused by #24596

Thanks for the update. Overall LGTM.
Let's wait #24596 merged and rebase it to trigger the CI again.

[masteryhx]

Thanks for the update.
LGTM.