add rtdetr m (#8181)

configs/rtdetr/README.md

@@ -18,6 +18,7 @@ RT-DETR是第一个实时端到端目标检测器。具体而言，我们设计
 
 | Model | Epoch | backbone  | input shape | $AP^{val}$ | $AP^{val}_{50}$| Params(M) | FLOPs(G) |  T4 TensorRT FP16(FPS) | Pretrained Model | config |
 |:--------------:|:-----:|:----------:| :-------:|:--------------------------:|:---------------------------:|:---------:|:--------:| :---------------------: |:------------------------------------------------------------------------------------:|:-------------------------------------------:|
+| RT-DETR-R50-scaled | 6x |  ResNet-50 | 640 | 51.3 | - | - | - | 145 | [download](https://bj.bcebos.com/v1/paddledet/models/rtdetr_r50vd_m_6x_coco.pdparams) | [config](./rtdetr_r50vd_m_6x_coco.yml)
 | RT-DETR-R50 | 6x |  ResNet-50 | 640 | 53.1 | 71.3 | 42 | 136 | 108 | [download](https://bj.bcebos.com/v1/paddledet/models/rtdetr_r50vd_6x_coco.pdparams) | [config](./rtdetr_r50vd_6x_coco.yml)
 | RT-DETR-R101 | 6x |  ResNet-101 | 640 | 54.3 | 72.7 | 76 | 259 | 74 | [download](https://bj.bcebos.com/v1/paddledet/models/rtdetr_r101vd_6x_coco.pdparams) | [config](./rtdetr_r101vd_6x_coco.yml)
 | RT-DETR-L | 6x |  HGNetv2 | 640 | 53.0 | 71.6 | 32 | 110 | 114 | [download](https://bj.bcebos.com/v1/paddledet/models/rtdetr_hgnetv2_l_6x_coco.pdparams) | [config](rtdetr_hgnetv2_l_6x_coco.yml)

configs/rtdetr/rtdetr_r50vd_m_6x_coco.yml

+_BASE_: [
+  '../datasets/coco_detection.yml',
+  '../runtime.yml',
+  '_base_/optimizer_6x.yml',
+  '_base_/rtdetr_r50vd.yml',
+  '_base_/rtdetr_reader.yml',
+]
+
+weights: output/rtdetr_r50vd_m_6x_coco/model_final
+find_unused_parameters: True
+log_iter: 200
+
+HybridEncoder:
+  hidden_dim: 256
+  use_encoder_idx: [2]
+  num_encoder_layers: 1
+  encoder_layer:
+    name: TransformerLayer
+    d_model: 256
+    nhead: 8
+    dim_feedforward: 1024
+    dropout: 0.
+    activation: 'gelu'
+  expansion: 0.5
+  depth_mult: 1.0
+
+RTDETRTransformer:
+  eval_idx: 2 # use 3th decoder layer to eval