Add new model: GeoLM
Author: zekun-li
Pull request: yes

# What does this PR do?

Add a new model called **GeoLM** into the Transformer library. GeoLM is a language model based on BERT that facilitates **geospatial understanding** in NL documents. It is pretrained on world-wide OpenStreetMap (OSM), WikiData and Wikipedia data, and can be adapted to various geospatial related downstream tasks such as **toponym recognition** and **toponym linking**. 

## Model Weights:
* Pretrained GeoLM (ready-to-use for zero-shot toponym linking): [zekun-li/geolm-base-cased](https://huggingface.co/zekun-li/geolm-base-cased)
* Fine-tuned GeoLM for toponym recognition: [zekun-li/geolm-base-toponym-recognition](https://huggingface.co/zekun-li/geolm-base-toponym-recognition)

## Open source status

- [x]  The model implementation is available in this PR
- [x]  The model weights are available in HuggingFace model hub

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## 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: @ArthurZucker and @younesbelkada

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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: @sgugger

Integrations:

- deepspeed: HF Trainer/Accelerate: @pacman100
- ray/raytune: @richardliaw, @amogkam

Documentation: @sgugger, @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: @sgugger
- TensorFlow: @Rocketknight1

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Comments:
This PR contains redundant commits and failed test cases. I will fix them and create a new PR later.