[Feature] Support YOLOv5u inference

[RangeKing]

Motivation

1. Support YOLOv5u inference referring to ultralytics 8.0.26 new YOLOv5u models ultralytics/ultralytics#771
2. Unify all config links to the relative link

Model	mAPval 50-95 Official repo	mAPval 50-95 MMYOLO
YOLOv5nu	34.3	34.4
YOLOv5su	43.0	43.1
YOLOv5mu	49.0	49.1
YOLOv5lu	52.2	52.4
YOLOv5xu	53.2	53.3

[hhaAndroid]

@RangeKing Can other scale model inference be supported at the same time?

[RangeKing]

@RangeKing Can other scale model inference be supported at the same time?

Model	mAPval 50-95 Official repo	mAPval 50-95 MMYOLO
YOLOv5nu	34.3	34.4
YOLOv5su	43.0	43.1
YOLOv5mu	49.0	49.1
YOLOv5lu	52.2	52.4
YOLOv5xu	53.2	53.3