* Add cosine cool down lr updater
* Use ema hook
* Update decay mult
* Update configs.
* Update T2T-ViT readme and format all readme
* Update swin readme
* Update tnt readme
* Add docstring for `CosineAnnealingCooldownLrUpdaterHook`.
* Update t2t readme and metafile
* implement the conformer
* format code style
* format code style
* reuse the TransformerEncoderLayer in the vision_transformer.py
* Modify variable name
* delete unused params
* Remove warning info in Conformer head since it already exists in
Conformer.
* Rename some variables
* Add unit tests
* Use `getattr` instead of `get_submodule`.
* Remove some useless layers
* Refactor conformer and add configs
* Update configs and add metafile.
* Fix unit tests
* Update README
Co-authored-by: mzr1996 <mzr1996@163.com>
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