Re-run with reweighting only after unweighting step (cherry-picking to master)

This MR will cherry-pick the performance improvements from tmp-rerun-with-reweighting-after-unweighting+rel-2-2-11 for master.

• Note that cherry-picking d5fc7966 left out the changes to the Recola interface, which has not been merged into master yet. Mention this commit as soon as we have a MR for the Recola interface.