Clean up Ops Box and Losses implementations

[datumbox]

🚀 The feature

Currently losses such as cIoU, dIoU and gIoU reimplement functions that exist already on boxes ops. In addition they contain a lot of duplicate code that can be shared. Finally the testing strategy can be improved.

This ticket is about:

• Investigating ways to re-use code on Losses from boxes. This should happen without affecting the speed (See https://github.com/pytorch/vision/pull/5877#discussion_r858595615).
• Reduce the amount of code duplication between methods gIoU/dIoU/cIoU boxes and losses
• Align the testing strategy between the different similar methods and incorporate the comments at https://github.com/pytorch/vision/pull/5786#discussion_r857325564

cc @oke-aditya

[oke-aditya]

I'm on this :smile: (I think as per Phillip's comment I can't self assign, but feel free to assign me)