### 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
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Signed-off-by: Angazenn <supperccell@163.com>
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