* [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
* * fix typehint & docstring in sharder.py
* * update pipeline forward for GPT2Model
* * add test for pipeline forward of GPT2Model
* * add cache cleaning in gpt2 test
* * change assert to raise command
* [shardformer] support lazy init
* [shardformer] linear support lazy init
* [shardformer] embedding support lazy init
* [shardformer] norm support lazy init
* [shardformer] fused linear support lazy init
* [test] update shardformer test layer
* [test] shardformer with lazy init fit ddp
* [lazy] hotfix deepcopy of param
* [shardformer] fix bert policy and update test
* [shardformer] fix bloom policy and update test
* [shardformer] fix opt policy and update test
* [shardformer] fix t5 policy and update test
* [shardformer] fix gpt2 policy and update test
* [shardformer] fix llama policy and update test
Bin Jia