* Copy wandb param dict before training to avoid overwrites.

Copy the hyperparameter dict retrieved from wandb configuration before passing it to `train()`. Training overwrites parameters in the dictionary (eg scaling obj/box/cls gains), which causes the values reported in wandb to not match the input values. This is confusing as it makes it hard to reproduce a run, and also throws off wandb's Bayesian sweep algorithm.

* Cleanup
Co-authored-by: Glenn Jocher <glenn.jocher@ultralytics.com>