Need search config option to limit wall clock time spent on a given search

It seems some searches are effectively getting "stuck" during the GPU or filtering phase, currently both part of a single Parsl workflow step. It would be useful for us to be able to set a limit on how long we search before giving up. We should log what step we were on when we stop a search, and be sure to free GPU memory if it was on GPU during that time (probably not, but just in case).