* [shardformer/sequence parallel] Support sequence parallel for gpt2 (#4384)
* [sequence parallel] add sequence parallel linear col/row support (#4336)
* add sequence parallel linear col/row support
* add annotation
* add annotation
* add support for gpt2 fused qkv linear layer
* support sequence parallel in GPT2
* add docstring and note
* add requirments
* remove unused flash-attb
* modify flash attn test
* modify flash attn setting
* modify flash attn code
* add assert before divide, rename forward function
* [shardformer/test] fix gpt2 test with seq-parallel
* [shardformer/sequence parallel] Overlap input gather and grad computation during col backward (#4401)
* overlap gather input / grad computing during col backward
* modify test for overlap
* simplify code
* fix code and modify cuda stream synchronize
* [shardformer/sequence parallel] polish code
* first v of vit shardformer
* keep vit
* update
* vit shard add vitattention vitlayer
* update num head shard para
* finish test for vit
* add new_model_class & postprocess
* add vit readme
* delete old files & fix the conflict
* fix sth
* add dropout layer, add dropout test
* modify seed manager as context manager
* add a copy of col_nn.layer
* add dist_crossentropy loss; separate module test
* polish the code
* fix dist crossentropy loss
* add dropout layer, add dropout test
* modify seed manager as context manager
* add a copy of col_nn.layer
* add dist_crossentropy loss; separate module test
* polish the code
* fix dist crossentropy loss
Bin Jia