[Attention] remove cum_offsets from atten, and use cu_seqlens_q (#2870)
* [Sync] Update to latest code * Add new code files * Add new code files * update code * Try to fix build.sh * Try to fix build.sh * Update code * Update requirements.txt * Update code --------- Co-authored-by: Jiang-Jia-Jun <jiangjiajun@baidu.com>