[Feature] Enable PP + SP for llama (#5868)

* 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

* use a one cross entropy func for all shardformer models

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

colossalai/shardformer/layer/__init__.py

@@ -3,7 +3,7 @@ from .attn import AttnMaskType, ColoAttention
 from .dropout import DropoutForParallelInput, DropoutForReplicatedInput
 from .embedding import Embedding1D, PaddingEmbedding, VocabParallelEmbedding1D
 from .linear import Linear1D_Col, Linear1D_Row, PaddingLMHead, VocabParallelLMHead1D
-from .loss import cross_entropy_1d
+from .loss import cross_entropy_1d, dist_cross_entropy
 from .normalization import FusedLayerNorm, FusedRMSNorm, LayerNorm, RMSNorm
 from .parallel_module import ParallelModule
 from .qkv_fused_linear import FusedLinear1D_Col, GPT2FusedLinearConv1D_Col, GPT2FusedLinearConv1D_Row
@@ -18,6 +18,7 @@ __all__ = [
     "DropoutForParallelInput",
     "DropoutForReplicatedInput",
     "cross_entropy_1d",
+    "dist_cross_entropy",
     "BaseLayerNorm",
     "LayerNorm",
     "RMSNorm",