[feat] Add distributed lamb; minor fixes in DeviceMesh and comments

[Edenzzzz]

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📝 What does this PR do?

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1. Add distributed Lamb supporting Tensor Parallel and ZeRO stage 2
2. Add bias correction to Lamb
3. Fixed DeviceMesh failing to map rank to "squeezable" axis (e.g. axis 1 in mesh shape (4, 1) )
4. Minor improvements on comments.

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