Refactor progress bars

[PhilippvK]

The --progress option is available for the mlonmcu flow and mlonmcu setup commands.

I modified their format string to get rid of the estimated remaining which which is not useful for our approach. However it would be great if we could add an indicator of how long is the underlying process running.

[PhilippvK]

The time spent until the last increment is now displayed after progress bar. It is therefore not incrementing continuously.

Also there is a "bug" that the progress bar does not update at all when a step was very short. This should be fixable by tuning some of the configured latencies.