Report results as soon as possible, not only after all data points are collected

[smarr]

This is especially useful for round-robin or random execution

[smarr]

Also useful: try to parse output already while it is running, to persist data, empty output buffers, and possibly indicate progress more fine-grained, i.e., on iteration level, not just invocation level.

[smarr]

This is related to #132 and should be considered with it.