目标检测模型离线量化示例

[lizexu123]

修改为Paddle2.6和Paddleslim2.6的组合，并添加了yolov3_r50vd_dcn_270e_coco示例

[paddle-bot[bot]]

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:white_check_mark: lizexu123
:x: RachelXu7
:x: ceci3
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