Merge branch 'lean_tasks' into 'master'
Lean tasks First step in cleaning up our tasks, remove the `tic`, `toc`, and `rid` fields, i.e. make them optional for debugging. These values are currently only being used for: * Task reweighting with wall-clock values, which is dubious at best and has been removed for now, * Repartitioning, which can also be done with the pre-computed task cost estimates. * Some error checking in the scheduler, but it's all cases that would cause failures elsewhere, so they won't be missed, * Generating task plots, which is still possible if configured with `--enable-task-debugging`. See merge request !273