[Misc] Use deprecated for seed_everything

[DarkLight1337]

Purpose

Use deprecated decorator to emit a warning message. Also changed the removal date to v0.15 as we are close to v0.14 already.

I also found various benchmarks that use the deprecated method, so I've updated them accordingly.

cc @wangxiyuan

Test Plan

Test Result

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• The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
• The test plan, such as providing test command.
• The test results, such as pasting the results comparison before and after, or e2e results
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• (Optional) Release notes update. If your change is user facing, please update the release notes draft in the Google Doc.

[gemini-code-assist]

Code Review

This pull request correctly updates the deprecation mechanism for seed_everything to use the @deprecated decorator, aligning with the project's policy. However, by removing the explicit logging call, the deprecation warning may become invisible to users due to Python's default warning handling. I've recommended re-introducing a log message to ensure users are properly notified of the change, which seems to be in the spirit of the deprecation policy that mentions both log output and the decorator.

[wangxiyuan]

Thanks, it's better. And the doc should be update https://github.com/vllm-project/vllm/blob/main/docs/design/plugin_system.md#deprecation-announcement

[DarkLight1337]

Updated. Also updated benchmarks that use the deprecated method.

[mergify]

Documentation preview: https://vllm--31780.org.readthedocs.build/en/31780/

[Yikun]

Thank you for your support of the plugin dev experience! LOL!