### What this PR does / why we need it?
Refactor PCP & DCP patches in UTs: Merge and reuse communication groups
and communication function patches to reduce code duplication.
### Does this PR introduce _any_ user-facing change?
No
- vLLM version: v0.13.0
- vLLM main:
45c1ca1ca1
Signed-off-by: QiuChunshuo <qiuchunshuo@huawei.com>