* fix(examples): exit program if load_param, load_model failed for clear error messsage

* ignore .cache dir for clangd

* check non-zero instead of -1 for load functions

* Reduce yolov5 post time.

sigmoid(X)<1, 
IF：box_confidence<prob_threshold
THEN: confidence=box_confidence*sigmoid(class_score)<box_confidence<prob_threshold,
So there is no need to calculate class_score when box_confidence<prob_threshold，and the confidence of most anchors is lower than the prob_threshold.

Co-authored-by: UNeedCryDear <UNeedCryDear@users.noreply.github.com>