refactor: explicit template for image classification

[ydcjeff]

Explicit template code instead of extending from base template. This PR

• Add wandb logging system
• Add save_best_model_by_val_score and setup_common_training_handlers
• Removed metadata.json and generate_metadata.json and define template config in {template}_sidebar.py
• Renamed {template}_config.py to {template}_sidebar.py
• Commented out amp_mode since ignite latest is v0.4.4
• device is automatically determined via idist.device()

cc: @pytorch-ignite/project-leaders

[trsvchn]

So, no more inheritance?

[ydcjeff]

So, no more inheritance?

Yes, I chose that way as I found overwriting some parts looks a little weird to me and make easy for contributors who might not know jinja. This would require almost same and more work if templates need to update same configs (like supporting hydra)

What do you think ?

[trsvchn]

I like it, I am not big fan of inheritance as a concept)

[trsvchn]

LGTM!