Add new IFluidHandler for capabilities. (#2942)

Old fluid system is deprecated and slated for removal in the next cleanup cycle.

src/main/java/net/minecraftforge/fluids/FluidStack.java

@@ -174,12 +174,7 @@ public class FluidStack
             return false;
         }
 
-        if (other.getItem() instanceof IFluidContainerItem)
-        {
-            return isFluidEqual(((IFluidContainerItem) other.getItem()).getFluid(other));
-        }
-
-        return isFluidEqual(FluidContainerRegistry.getFluidForFilledItem(other));
+        return isFluidEqual(FluidUtil.getFluidContained(other));
     }
 
     @Override