add RGPR data augmentation for person reid

[AlphaPlusTT]

Add RGPR data augmentation for person reid(An Effective Data Augmentation for person re-identification(https://arxiv.org/abs/2101.08533))
mgn_repvgg_wo_RGPR(epoch 60):
rank1: 90.44, mAP: 81.56
mgn_repvgg_w_RGPR(epoch 60):
rank1: 90.66, mAP: 82.16
mgn_repvgg_w_RGPR(epoch 120):
rank1: 91.07, mAP: 82.18

[AlphaPlusTT]

There's nothing to change, but if you want to use RGPR for a better performance, you should double train epochs

[L1aoXingyu]

Thank you so much! Did you have experiment results with resnet50?

[AlphaPlusTT]

Not yet, but i can give a try :)