Function execute 

pub fn execute(
    store: &Store,
    home: &Path,
    cfg: &Config,
    over: &Overrides,
    runs: Vec<Run>,
    done: impl FnMut(&Run),
) -> Result<Vec<Run>>

Runs queued runs, at most max_parallel at once, starting a run only while the batch stays within batch_budget. done sees each run as it finishes.