Show current duration

Shows current test duration and flag whether it's new/removed or slowdown entry (`+`, `-`, `!`). Doesn't show slowdown entry for new/removed entries (because they match current duration).

Example output:

```
               Current     Test                                  
  Slowdown     duration    (! slowdown, + new entry, - removed)  
============ ============ =======================================
                 1.7830 s   + CENSORED
    0.9209 s     1.5999 s   ! CENSORED
                 0.7722 s   + CENSORED
    0.7640 s     1.2319 s   ! CENSORED
                 0.0002 s   + CENSORED
   -0.0001 s     0.0002 s     CENSORED
                            - CENSORED
                            - CENSORED

Total slowdown from worst 680 changes
============
  190.2622 s
```