[Draft] Flink 2.0 support

[Abacn]

Fix #36947

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[gemini-code-assist]

Summary of Changes

Hello @Abacn, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces initial support for Apache Flink 2.0 within the Apache Beam Flink Runner. It establishes a new Flink 2.0-specific module, adapting the build system and core runner components to align with Flink's updated API, notably the deprecation of the DataSet API. This ensures forward compatibility and leverages the latest Flink features for Beam pipelines.

Highlights

• Flink 2.0 Module Introduction: A new dedicated module (runners/flink/2.0) has been introduced to house Flink 2.0 specific runner implementations, separating it from previous Flink versions.
• Build System Adaptation: The gradle.properties file now includes Flink 2.0 in the list of supported versions. The flink_runner.gradle build script has been updated to manage version-specific source and resource overrides, and to enforce Java 11 for Flink 2.x builds. It also conditionally includes the flink-java dependency only for Flink 1.x versions, reflecting the removal of the DataSet API in Flink 2.0.
• Core Runner Component Updates: New Java files have been added under the runners/flink/2.0/src/main/java directory. These files implement Flink 2.0-compatible execution environments, pipeline options, translators, and DoFn operators, adapting to the latest Flink API changes.
• Job Server Configuration: Dedicated build files for the Flink 2.0 job server and job server containers have been added, including updated Docker image naming logic to correctly identify Flink 2.0 job servers.
• Pipeline Options Documentation Updates: The documentation for Flink pipeline options (both Java and Python) has been updated. This includes the removal of deprecated options like failOnCheckpointingErrors and reIterableGroupByKeyResult, the update of stateBackend descriptions, and the addition of the tolerableCheckpointFailureNumber option.

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