API C LegendaryCrafting.GetRuneforgeLegendaryUpgradeCost

Needs summary.
 cost = C_LegendaryCrafting.GetRuneforgeLegendaryUpgradeCost(runeforgeLegendary, upgradeItem)
==Arguments==
:;runeforgeLegendary:
:;upgradeItem:
==Returns==
:;cost:
==Patch changes==