[Mistral] Mistral-7B-v0.1 support
Author: Bam4d
Pull request: yes

# What does this PR do?

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Support for Mistral 7B models 

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Fixes # (issue)


## Before submitting
- [x] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
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- [x] Did you write any new necessary tests?


## Who can review?

Anyone in the community is free to review the PR once the tests have passed. Feel free to tag
members/contributors who may be interested in your PR.

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Models:

- text models: @ArthurZucker and @younesbelkada
- vision models: @amyeroberts
- speech models: @sanchit-gandhi
- graph models: @clefourrier

Library:

- flax: @sanchit-gandhi
- generate: @gante
- pipelines: @Narsil
- tensorflow: @gante and @Rocketknight1
- tokenizers: @ArthurZucker
- trainer: @muellerzr and @pacman100

Integrations:

- deepspeed: HF Trainer/Accelerate: @pacman100
- ray/raytune: @richardliaw, @amogkam
- Big Model Inference: @SunMarc
- quantization (bitsandbytes, autogpt): @SunMarc and @younesbelkada

Documentation: @stevhliu and @MKhalusova

HF projects:

- accelerate: [different repo](https://github.com/huggingface/accelerate)
- datasets: [different repo](https://github.com/huggingface/datasets)
- diffusers: [different repo](https://github.com/huggingface/diffusers)
- rust tokenizers: [different repo](https://github.com/huggingface/tokenizers)

Maintained examples (not research project or legacy):

- Flax: @sanchit-gandhi
- PyTorch: See Models above and tag the person corresponding to the modality of the example.
- TensorFlow: @Rocketknight1

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Comments:
Failing test is expected, you can add the `configuration_mistral` file to the `not_doctested.txt` file. 
The error: 
```python 
failed on setup with "worker 'gw0' crashed while running 'src/transformers/models/mistral/configuration_mistral.py::transformers.models.mistral.configuration_mistral.MistralConfig'"
worker 'gw0' crashed while running 'src/transformers/models/mistral/configuration_mistral.py::transformers.models.mistral.configuration_mistral.MistralConfig'
``` 
is just from trying to init a too big model for the runner! (Llama also had this issue) 

The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_26447). All of your documentation changes will be reflected on that endpoint.