Grey box optimization

Two options:

1: propulator passes additional infrastructure, like a maximum loss and time derived from the current population to the blackbox, which can use this information for pruning

2: the blackbox yields its current loss back to the propulator so it can decide whether to continue running the blackbox

No files, tests, or entry points are named. Start by comparing the two proposed interfaces and clarifying which approach should be pursued; done requires a resolved design choice and agreed implementation scope.

Written by the indexing model from the issue text.