### What this PR does / why we need it? The current implementation of FIA will introduce an `to_list` operation for actual_seq_lengths_q and seq_lens,which comsumes extra time. These operation can be moved earlier into `build` operation of attention metadata. ### Does this PR introduce _any_ user-facing change? No. ### How was this patch tested? - vLLM version: v0.11.0rc3 - vLLM main: https://github.com/vllm-project/vllm/commit/v0.11.0 --------- Signed-off-by: Angazenn <supperccell@163.com>