add rtdetr_ptq_demo (#1745)

example/post_training_quantization/detection/configs/rtdetr_ptq.yaml

+
+input_list: ['im_shape', 'image', 'scale_factor']
+model_dir: ./rtdetr_r50vd_6x_coco
+model_filename: model.pdmodel
+params_filename: model.pdiparams
+metric: COCO
+num_classes: 80
+  
+
+# Datset configuration
+TrainDataset:
+  !COCODataSet
+    image_dir: train2017
+    anno_path: annotations/instances_train2017.json
+    dataset_dir: /dataset/coco/
+
+EvalDataset:
+  !COCODataSet
+    image_dir: val2017
+    anno_path: annotations/instances_val2017.json
+    dataset_dir: /dataset/coco/
+
+worker_num: 0
+
+# preprocess reader in test
+EvalReader:
+  sample_transforms:
+    - Decode: {}
+    - Resize: {target_size: [640, 640], keep_ratio: False, interp: 2}
+    - NormalizeImage: {mean: [0., 0., 0.], std: [1., 1., 1.], norm_type: none}
+    - Permute: {}
+  batch_size: 8
+  shuffle: false
+  drop_last: false