[Feature] Zigzag Ring attention (#5905)

* halfway

* fix cross-PP-stage position id length diff bug

* fix typo

* fix typo

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* unified cross entropy func for all shardformer models

* remove redundant lines

* add basic ring attn; debug cross entropy

* fwd bwd logic complete

* fwd bwd logic complete; add experimental triton rescale

* precision tests passed

* precision tests passed

* fix typos and remove misc files

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* add sp_mode to benchmark; fix varlen interface

* update softmax_lse shape by new interface

* change tester name

* remove buffer clone; support packed seq layout

* add varlen tests

* fix typo

* all tests passed

* add dkv_group; fix mask

* remove debug statements

---------

Co-authored-by: Edenzzzz <wtan45@wisc.edu>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

colossalai/legacy/moe/openmoe/model/openmoe_policy.py

@@ -171,7 +171,7 @@ class OpenMoeForCausalLMPolicy(OpenMoePolicy):
         policy = super().module_policy()
 
         if self.shard_config.enable_tensor_parallelism:
-            # add a new item for casual lm
+            # add a new item for causal lm
             # TODO: recursively assign ep group foe all modules
             new_item = {
                 OpenMoeForCausalLM: ModulePolicyDescription(