DetectMultiBackend() default stride=32 (ultralytics#7342)

* set common default stride as 32

* restore default stride, and set it on argument optional

* fix wrong use of opt

* fix missing parameter of stride

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* fix format of parameters

* Update val.py

* Update common.py

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Glenn Jocher <glenn.jocher@ultralytics.com>

models/common.py

@@ -296,7 +296,7 @@ def __init__(self, weights='yolov5s.pt', device=torch.device('cpu'), dnn=False,
         super().__init__()
         w = str(weights[0] if isinstance(weights, list) else weights)
         pt, jit, onnx, xml, engine, coreml, saved_model, pb, tflite, edgetpu, tfjs = self.model_type(w)  # get backend
-        stride, names = 64, [f'class{i}' for i in range(1000)]  # assign defaults
+        stride, names = 32, [f'class{i}' for i in range(1000)]  # assign defaults
         w = attempt_download(w)  # download if not local
         fp16 &= (pt or jit or onnx or engine) and device.type != 'cpu'  # FP16
         if data:  # data.yaml path (optional)