Improve workers cli log

[kobenguyent]

Currently, when running tests using run-workers, we see something like this in cli logs, which are not really well captured.

[03]   ✔ Fetch a specific account in 2628ms
[01]   ✔ Fetch a specific account in 2828ms
[02]   ✔ Fetch a specific account in 268ms

Improvements:

• portrait better the worker index that is running tests
• add feature name before scenario name to get more transparency, there would be the case which two different features have the same scenario name