v0.2.6
[pipeline] refactor pipeline (#679)
[hotfix] fix an assertion bug in base schedule. (#1250)
[hotfix]fix some bugs caused by refactored schedule. (#1148)
[NFC] polish colossalai/engine/schedule/_pipeline_schedule.py code style (#2744)
[engin/schedule] use p2p_v2 to recontruct pipeline_schedule (#1408)