### What this PR does / why we need it?
To intuitively show the effect of the eplb algorithm, we print the
expert heat before and after eplb.
### Does this PR introduce _any_ user-facing change?
### How was this patch tested?

- vLLM version: v0.16.0
- vLLM main:
15d76f74e2
Signed-off-by: shenchuxiaofugui <1311027364@qq.com>