store systematically in work-dir the results files of metrics

[GS6902]

Hi,

I would like to store for each executions the results of some metrics class that generate a png. It's my own class but it is derivated from the the dota_metric class
I would like the same comportment that the visualization hook, if nothing is specified, please store that in work_dir/timestamp/my_metric

I have thought to use a outfile_prefix argument But during parsing of the config file, work dir do not exist yet
I suppose I should use a hook that seem to gather all information at the same place like the visualization hook class or WandB hook.

Is there a simpler way to do something similar maybe using only the configuration ?