Incorrect padding_side Setting as 'left' in Llama Family Model
### System Info

- `transformers` version: 4.30.2
- Platform: Linux-5.15.0-1041-azure-x86_64-with-glibc2.29
- Python version: 3.8.10
- Huggingface_hub version: 0.16.2
- Safetensors version: 0.3.1

### Who can help?

text models: @ArthurZucker and @younesbelkada generate: @gante

### Information

- [ ] The official example scripts
- [X] My own modified scripts

### Tasks

- [ ] An officially supported task in the `examples` folder (such as GLUE/SQuAD, ...)
- [X] My own task or dataset (give details below)

### Reproduction

When utilizing the Llama Family Model for batch generation, an issue arises due to the lack of a padding token. To clarify, the original model uses pad_id = -1, implying the absence of a padding token. This logic is infeasible for our scenario.

Here is our proposed solution:

Firstly, a padding token should be added using the command tokenizer.add_special_tokens({"pad_token":"<pad>"}), following which the token embedding must be resized accordingly. It's essential to also set model.config.pad_token_id. The embed_tokens layer of the model is initialized with self.embed_tokens = nn.Embedding(config.vocab_size, config.hidden_size, self.config.padding_idx). This ensures that encoding the padding token outputs zeros. Therefore, passing it during initialization is recommended.


### Expected behavior

Another important aspect is setting the padding_side to 'right'. This is crucial for correct padding direction.
Hey! Indeed, as it was written in the documentation a padding token is required. Seems that by default the padding side is set to `left`. We cannot update the `tokenization` file (for backward compatibility reasons) but we can update the tokenizers online to make sure they use `padding_side = right` by default. <|||||>> Hey! Indeed, as it was written in the documentation a padding token is required. Seems that by default the padding side is set to `left`. We cannot update the `tokenization` file (for backward compatibility reasons) but we can update the tokenizers online to make sure they use `padding_side = right` by default.

Great, I would be nice to update the default padding_side of those model.