[Quantization] Add new PaddleSeg models quantization support. (#953)

* Fix links in readme

* Fix links in readme

* Update PPOCRv2/v3 examples

* Update auto compression configs

* Add neww quantization  support for paddleclas model

* Update quantized Yolov6s model download link

* Improve PPOCR comments

* Add English doc for quantization

* Fix PPOCR rec model bug

* Add  new paddleseg quantization support

* Add  new paddleseg quantization support

* Add  new paddleseg quantization support

* Add  new paddleseg quantization support

tools/common_tools/auto_compression/configs/segmentation/unet_quant.yaml

@@ -0,0 +1,38 @@
+Global:
+  model_dir: ./Unet_cityscapes_without_argmax_infer/
+  format: paddle
+  model_filename: model.pdmodel
+  params_filename: model.pdiparams
+  qat_image_path: ./train_stuttgart
+  ptq_image_path: ./train_stuttgart
+  input_list: ['x']
+  qat_preprocess: ppseg_cityscapes_qat_preprocess
+  ptq_preprocess: ppseg_cityscapes_ptq_preprocess
+  qat_batch_size: 2
+
+
+Distillation:
+  alpha: 1.0
+  loss: l2
+  node:
+  - conv2d_37.tmp_1
+
+QuantAware:
+  onnx_format: True
+  quantize_op_types:
+  - conv2d
+  - depthwise_conv2d
+
+
+TrainConfig:
+  epochs: 10
+  eval_iter: 180
+  learning_rate: 0.0005
+  optimizer_builder:
+    optimizer:
+      type: SGD
+    weight_decay: 4.0e-05
+
+PTQ:
+  calibration_method: 'avg'   # option: avg, abs_max, hist, KL, mse
+  skip_tensor_list: None