### What this PR does / why we need it?
Add local running multi-node nightly test case guide, help running
locally at developer env.
### Does this PR introduce _any_ user-facing change?
NA
### How was this patch tested?
Test with local running multi-node test.
Using this document can successfully start multi-node night e2e in
locall
- vLLM version: v0.12.0
- vLLM main:
ad32e3e19c
---------
Signed-off-by: leo-pony <nengjunma@outlook.com>