### What this PR does / why we need it?
4/N EAGLE refactor plan devided into many parts, this PR is the first
change, which modifies the attn_metadata update method by modifying
common_metadata and then rebuilding the code.
### Does this PR introduce _any_ user-facing change?
ut
### How was this patch tested?
no
- vLLM version: v0.13.0
- vLLM main:
bde38c11df
---------
Signed-off-by: lilinsiman <lilinsiman@gmail.com>
Signed-off-by: Zetong Li <slippersss@126.com>
Co-authored-by: Zetong Li <slippersss@126.com>