add model resources for CPMAnt
Author: pioliverse
Pull request: yes

# What does this PR do?

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- **introduction**: [CPM-Ant](https://github.com/OpenBMB/CPM-Live/tree/cpm-ant/cpm-live) is an open-source Chinese pre-trained language model (PLM) with 10B parameters.
- **task**: We add code, tests and docs for cpmant model. The model can be used for text generation with "text-generation" pipeline.


## Before submitting
- [x] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
- [x] Did you read the [contributor guideline](https://github.com/huggingface/transformers/blob/main/CONTRIBUTING.md#start-contributing-pull-requests),
      Pull Request section?
- [ ] Was this discussed/approved via a Github issue or the [forum](https://discuss.huggingface.co/)? Please add a link
      to it if that's the case.
- [x] Did you make sure to update the documentation with your changes? Here are the
      [documentation guidelines](https://github.com/huggingface/transformers/tree/main/docs), and
      [here are tips on formatting docstrings](https://github.com/huggingface/transformers/tree/main/docs#writing-source-documentation).
- [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.
@ArthurZucker @younesbelkada

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Models:

- text models: @ArthurZucker and @younesbelkada
- vision models: @amyeroberts and @NielsRogge
- speech models: @sanchit-gandhi

Library:

- flax: @sanchit-gandhi
- generate: @gante
- pipelines: @Narsil
- tensorflow: @gante and @Rocketknight1
- tokenizers: @ArthurZucker
- trainer: @sgugger

Integrations:

- deepspeed: @stas00
- ray/raytune: @richardliaw, @amogkam

Documentation: @sgugger and @stevhliu

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: @sgugger
- TensorFlow: @Rocketknight1

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Comments:
The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_20711). All of your documentation changes will be reflected on that endpoint.

> Thanks for addressing some of the comments! Some tests are still failing for few reasons 1- You are assigning an attribute that uses `torch` on the config file, I suspect this is not needed 2- You need to make sure that integration tests are not failing, I suggest you to run `pytest tests/models/cpmant/test_modeling_cpmant.py` and understand why these tests are failing. Thanks again for your efforts!

Some new tests have been added in ```test_modeling_cpmant.py``` .