Update dashboards to use a macro for time evals

[EatMoreChicken]

Each panel in the dashboard has a hard-coded eval to extract as human-readable time from epoch time. Build a macro that can accomplish this and update the dashboards to use it.

[EatMoreChicken]

I actually don't remember why I had this as an issue in my notes. I don't see any evals that we are doing on the time itself, but math on the time. Anyway, I'll keep this in here if we find it.