When writing outputs or logs, if already exists, append with something

[madeline-scyphers]

If specified output dir already exists, then append it with something unique. This could be a unique number (counting upwards so that if it keeps happening do it again. I.e. if output exists -> output_1 -> output_2 -> output_3, etc.) Or this could be a timestamp that we always do (if output dir := output, then we save to output_)