[FLINK-36744][docs] Document operator's FlinkVersion compatibility policy

[arvindKandpal-ksolves]

What is the purpose of the change (FLINK-36744)

This pull request documents the FlinkVersion compatibility policy introduced
in Flink Kubernetes Operator 1.7, which was previously only discoverable in
source code (FlinkVersion.java) and not mentioned in the official documentation.

Adds a new "Flink Version Compatibility" section to the Compatibility Guarantees
documentation page explaining the last-4-minor-versions policy and linking to
FlinkVersion.java for the current supported version list.

Also updates the Chinese translation (content.zh) with full translated content
and the new section.

Brief change log

• Added "Flink Version Compatibility" section to docs/content/docs/operations/compatibility.md
• Added "Flink 版本兼容性" section to docs/content.zh/docs/operations/compatibility.md
• Translated existing English content to Chinese in content.zh/docs/operations/compatibility.md

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 changes to the CustomResourceDescriptors: no
• Core observer or reconciler logic that is regularly executed: no

Documentation

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

[arvindKandpal-ksolves]

Hi @Dennis-Mircea , Please review it whenever have time.

[Dennis-Mircea]

This part will be covered as part of FLINK-39571. This PR can be closed.

[arvindKandpal-ksolves]

Hi @Dennis-Mircea, thank you for the review!

This ticket is open since November 2024, so if you are okay with it, we can merge this PR and close FLINK-36744, and the remaining complete docs improve parts can be covered under FLINK-39571.

Let me know what you think!