### What this PR does / why we need it? The basic configs are extracted and reused for eplb UT. This is done so that if the basic configs are changed later, eplb UT does not need to be modified repeatedly. ### Does this PR introduce _any_ user-facing change? ### How was this patch tested? - vLLM version: v0.15.0 - vLLM main: https://github.com/vllm-project/vllm/commit/v0.15.0 Signed-off-by: bigsir007 <xujiacheng12@huawei.com> Co-authored-by: bigsir007 <xujiacheng12@huawei.com>