[#691,114,630] 0 cost unlimited channeling via Pyro Pact

bug # ss: https://i.imgur.com/1HAMU0f.png

https://www.youtube.com/watch?v=Kx7yQc940KM
https://www.youtube.com/watch?v=0zE6AD_yKN4

If the first skill you use through a portal is a channel it's entirely free until you use a non-channeled skill with a mana cost, whether it's a spell or attack. Rezoning or dying will reset the behaviour. Confirmed that it affects Bonestorm (spell), Detonating Arrow & Gathering Storm (attacks), so likely affects all channels.

Using a spell that's entirely paid via life (Burden of Shadows) does not induce Flame to start accumulating.

Sigil of Power also still counts the channeling skill as spending that mana, and stacks to 4 stages by the 3 second mark.

0:00 normal behaviour
0:55 rezone, free channel in h/o
1:29 rezone, free channel in map
1:43 cast LW to trigger spend, costs flame again
1:53 rezone, free channel in h/o

If it's unreproducible, here's my setup: https://pobb.in/tt-MC29cbpsT
the life loss is from extraction support