Document the Coscheduling integration and --node-lock-retry-timeout

[lin121291]

What is missing or unclear:

Project-HAMi/HAMi#2066 added PodGroup-aware node lock retry and a new
--node-lock-retry-timeout flag. The flag is not documented anywhere, and
there is no guide for running HAMi with the scheduler-plugins Coscheduling
plugin.

Where it should go (existing page, or a new page):

• New page userguide/coscheduling/how-to-use-coscheduling.md, under
  "Scheduler Integrations" alongside Kueue and KAI Scheduler.
• A new extender arguments section in userguide/configure.md.
• Chinese translations for both.

Why this would help:

Anyone combining gang scheduling with HAMi today has to work the setup out
from source.

[coderabbitai]

🔗 Related PRs

#604 - docs: fix scheduler policy flag, schedulerName case, and stale link [merged]
#612 - docs: fix kai-scheduler hamicore install flags (guide + blog + zh) [merged]
#613 - docs: add NVIDIA CDI configuration guide [merged]
#654 - docs(tutorials): add Lab 11 — Run SGLang on HAMi GPU Shares [open]
#722 - docs(tutorials): add KAI Scheduler + HAMi-core lab on nvml-mock [open]

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