[Feature] add_scalar in logger_hook for after_test_epoch

[AwePhD]

What is the feature?

Hello,

Why the method Visualizer.add_scalars is only called in after_val_epoch and not it after_test_epoch?

I think it can be a good thing to add this feature for test with some vis_backends for logs tracking (WandB, MLFlow, Tensorboard ...)

I made the edit locally of the after_test_epoch, I use a new attribute for the LoggerHook named log_test_metric_by_visualizer set by default to True.

What do you think about it? Would it be better to this in another hook? (I think it would be a bit weird since the logger hook already those kind of loggings.

Any other context?

No response