[Examples] Update train_unconditional.py to include logging argument for Wandb

[ash0ts]

Add logger flag to choose between tensorboard and wandb for a minimal implementation Removed remainder of logging code to rediscuss for future.

Hyperlinked is a commit which will show an example utilizing an extended form of the wandb logger which can log images and model checkpoints: LINK to branch: https://github.com/ash0ts/diffusers/tree/add-wandb-unconditional-image/examples/unconditional_image_generation

Refers to this PR: https://github.com/huggingface/diffusers/pull/1245

[HuggingFaceDocBuilderDev]

The documentation is not available anymore as the PR was closed or merged.