[FLINK-40574][build] Update SLF4J from 1.7.36 to 2.0.19

[piotrp]

What is the purpose of the change

Update of SLF4J dependency to current version:

• makes dependency management easier for projects that build on Flink or use Logback
• prevents possible issues if a library Flink depends on starts using new SLF4J APIs

Brief change log

Updated SLF4J 1.7.36 to 2.0.19. New version has compatible API, only Log4J binding must use a different dependency (log4j-slf4j-impl -> log4j-slf4j2-impl).

Verifying this change

This change is already covered by existing tests.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): yes
• 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: yes - for deployments that replace logging libraries
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? yes
• If yes, how is the feature documented? docs

Update to Chinese documentation is fully AI-generated.

---

Was generative AI tooling used to co-author this PR?

• Yes (please specify the tool below)

Generated-by: Claude Code

[flinkbot]

CI report:

• 86c5477 Azure: SUCCESS

Bot commands

The @flinkbot bot supports the following commands:

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

[spuru9]

Clean, well-scoped SLF4J 1.7.36 -> 2.0.19 bump: NOTICE files and EN/ZH docs are updated consistently.

minor: the commit message is just "Update SLF4J from 1.7.36 to 2.0.19" - missing the [FLINK-40574][build] prefix and Generated-by trailer that AGENTS.md asks for (both are present in the PR title/description, just not the actual commit). Worth fixing before merge.

[piotrp]

Prefix and trailer added

[spuru9]

LGTM

[Samrat002]

Why not use the latest version 2.26.1?

[piotrp]

Because this is about SLF4J, not Log4j. I didn't want to mix multiple changes in one PR.

Edit: and Log4j is already at 2.26.1...