perf report: summary.py: added --progress mode

Basically we compare `i` sample with the first reference sample (`0`). It is useful to compare different implementations/devices (samples represent different implementations).
This PR add the progress mode, when we compare `i` sample with the previous `i - 1` sample (or `i - k` if `i - k + 1` is missed/failed). This mode is useful to track changes "in time": samples represent different timestamps.