refactor(levels): use a gamecore timer to handle debris diseappearing

imperium-porcorum.love/scenes/levels/entities/debris.lua

@@ -4,9 +4,10 @@ local Debris = Entity:extend()
 
 function Debris:new(world, x, y, speed, dir, timelimit)
   Debris.super.new(self, world, "debris", x - 4, y - 4, 8, 8)
-  self.life = 0;
-  self.timer = 0
-  self.timelimit = timelimit or 2
+  local timelimit = timelimit or 2
+
+  self:addTimer("timelimit", timelimit)
+
   self:setMotionDirection(dir, speed)
   self:setGravityFlag(true)
   self:setBounceFactor(0.5)
@@ -31,9 +32,10 @@ function Debris:updateEnd(dt)
   if (isInsideView == false) then
     self:destroy()
   end
+end
 
-  self.timer = self.timer + dt
-  if (self.timer >= self.timelimit) then
+function Debris:timerResponse(timer)
+  if (timer == "timelimit") then
     self:destroy()
   end
 end