fix(sidebar): show timer of last run

[jpatovh]

Hello,

In the sidebar, the timer duration is calculated since the first run.

For example, if I run a workflow on monday, and I re-launch it on tuesday, the timer will show something like "26h38m".
We understand that our workflow run takes 26h38min to executed, instead of few minutes!

It'll make more sense to display the duration of the last run. What do you think?

Thx