add the detext to beta dataset preparer

[2019zhou]

Motivation

add the detext to beta dataset preparer

Modification

add the detext to the dataset_zoo and the add the DetextDetAnnParser

dataset_zoo/
├── detext
│ ├── metafile.yml
│ ├── textdet.py
│ ├── textrecog.py
│ └── textspotting.py

BC-breaking (Optional)

no

Use cases (Optional)

python tools/dataset_converters/prepare_dataset.py detext --task textdet --overwrite-cfg
python tools/dataset_converters/prepare_dataset.py detext --task textrecog --overwrite-cfg

Checklist

Before PR:

• I have read and followed the workflow indicated in the CONTRIBUTING.md to create this PR.
• Pre-commit or linting tools indicated in CONTRIBUTING.md are used to fix the potential lint issues.
• Bug fixes are covered by unit tests, the case that causes the bug should be added in the unit tests.
• New functionalities are covered by complete unit tests. If not, please add more unit test to ensure the correctness.
• The documentation has been modified accordingly, including docstring or example tutorials.

After PR:

• If the modification has potential influence on downstream or other related projects, this PR should be tested with some of those projects.
• CLA has been signed and all committers have signed the CLA in this PR.

[CLAassistant]

All committers have signed the CLA.

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[gaotongxiao]

It overall works great from my side, and there is some perspective to improve before we get it merged. :)

[gaotongxiao]

As dataset preparer will generate this config, we can remove it from this PR. Same for configs/textrecog/base/datasets/detext.py and configs/textspotting/base/datasets/detext.py

[gaotongxiao]

It seems that DetextDetAnnParser is exactly the same as ICDARTxtTextDetAnnParser? In this case, this implementation can be removed, and we can use reuse ICDARTxtTextDetAnnParser in Detext's config.