Add attn convertor.

[liyinbo]

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Motivation

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Modification

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BC-breaking (Optional)

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If so, please describe how it breaks the compatibility and how the downstream projects should modify their code to keep compatibility with this PR.

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Checklist

1. Pre-commit or other linting tools are used to fix the potential lint issues.
2. The modification is covered by complete unit tests. If not, please add more unit tests to ensure the correctness.
3. If the modification has a dependency on downstream projects of a newer version, this PR should be tested with all supported versions of downstream projects.
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[CLAassistant]

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[AllentDan]

Hi, @liyinbo
Please sign CLA before we can accept your contribution.

Please fix the lint issue. You can install pre-commit hook on your localhost like following:

pip install -U pre-commit
cd mmdeploy
pre-commit install

You can run pre-commit run --all-file to check whether there are lint errors

[lzhangzz]

For this to work on a SATRN model, ToTensorOCR and NormalizeOCR in preprocess pipeline must be reversed in order and transformed like

{
    "type": "Normalize",
    "mean": [123.675, 116.28, 103.53],  // scaled by 255
    "std": [58.395, 57.12, 57.375]      // scaled by 255
},
{
    "type": "ImageToTensor",
    "keys": ["img"]
}

[OpenMMLab-Assistant001]

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