5.4 PTR Update

- Changed the way we use vanish for openers with Sub. No longer
overrides existing methods and relies on existing data points.
- Base combo points for Sub shift towards Eviscerate damage in best
case scenarios again.
- t16 4pc Sub procs shift the damage from Backstab to Ambush like it
should.
- Pruned out Sub variables not being used.
- Added Marked for Death and Prep to the spell CD table. All requests
for them now go through get_spell_cd