Feature: Show set's total defense ratings and/or EHP

[petzku]

I'm not sure how feasible this is currently – it would require knowing the defense rating of every piece of gear – and it might clutter up the display a bit too much, but it could be fairly useful to e.g. know the differences in survivability when choosing what to spend one's tomestones on.

Notably, for a lot of jobs, this is actually two different numbers, as Maiming sets have more physical defense while Healing/Casting sets have more magical. Also, for tanks, this should consider the damage reduction from Tenacity as well as defense rating.

This might be sensible to implement as a new "sim" option, to have it not clutter the default display?