GitLab

- Accumulate encoder hidden state gradient to handle skip connection
- Correctly compute the number of layers in encoder / decoder for T5 model
- Ensure e weights are initialized the same way in embeddings
- Synchronize embedding gradients across encoder and decoder for T5 model
- Support for checkpoint loading and saving

Co-authored-by: shoeybi <shoeybim@gmail.com>
Co-authored-by: raulpuric <raulpuric@berkeley.edu>
Co-authored-by: jaredcasper <jaredcasper@gmail.com>
Co-authored-by: mpatwary <mostofa.patwary@gmail.com>
Co-authored-by: plegresl <plegresl@gmail.com>