Resolves beam rifle overtime issues (tgstation#83476)

## About The Pull Request

Ok so like, beam rifles send out tracer rounds right
We send out tracer rounds once every few seconds and if the mob or mouse
moves.
The problem is those tracer rounds are hitscan, and hitscan projectiles
don't like, wait to move.
So if I just drag my mouse a bunch I'm causin a bunch of hitscan
attempts.

This might be ok, but what happens if I do it in space (the place with
100s of turfs empty of things to hit).
Anyway let's do some tick checking in hitscan's while loop so it can't
eat seconds of cpu time uncontested

## Why It's Good For The Game


![image](https://github.com/tgstation/tgstation/assets/58055496/527b9bd1-4031-4a01-b4db-9e044270aa9b)


https://github.com/tgstation/tgstation/assets/58055496/2ce870f5-b65d-46e5-8dc3-11646c789290

code/modules/projectiles/guns/energy/beam_rifle.dm

@@ -71,6 +71,8 @@
  var/current_zoom_x = 0
  var/current_zoom_y = 0
 
+ var/obj/projectile/beam/beam_rifle/hitscan/aiming_beam/trace = null
+
 /obj/item/gun/energy/beam_rifle/apply_fantasy_bonuses(bonus)
  . = ..()
  delay = modify_fantasy_variable("delay", delay, -bonus * 2)
@@ -192,16 +194,19 @@
  if(diff < AIMING_BEAM_ANGLE_CHANGE_THRESHOLD && !force_update)
  return
  aiming_lastangle = lastangle
- var/obj/projectile/beam/beam_rifle/hitscan/aiming_beam/P = new
- P.gun = src
- P.wall_pierce_amount = wall_pierce_amount
- P.structure_pierce_amount = structure_piercing
- P.do_pierce = projectile_setting_pierce
+ // ONLY ONE at once (since fire can sleep)
+ if(trace)
+ QDEL_NULL(trace)
+ trace = new
+ trace.gun = src
+ trace.wall_pierce_amount = wall_pierce_amount
+ trace.structure_pierce_amount = structure_piercing
+ trace.do_pierce = projectile_setting_pierce
  if(aiming_time)
  var/percent = ((100/aiming_time)*aiming_time_left)
- P.color = rgb(255 * percent,255 * ((100 - percent) / 100),0)
+ trace.color = rgb(255 * percent,255 * ((100 - percent) / 100),0)
  else
- P.color = rgb(0, 255, 0)
+ trace.color = rgb(0, 255, 0)
  var/turf/curloc = get_turf(src)
 
  var/atom/target_atom = current_user.client.mouse_object_ref?.resolve()
@@ -211,8 +216,9 @@
  return
  targloc = get_turf_in_angle(lastangle, curloc, 10)
  var/mouse_modifiers = params2list(current_user.client.mouseParams)
- P.preparePixelProjectile(targloc, current_user, mouse_modifiers, 0)
- P.fire(lastangle)
+ trace.preparePixelProjectile(targloc, current_user, mouse_modifiers, 0)
+ trace.fire(lastangle)
+ trace = null
 
 /obj/item/gun/energy/beam_rifle/process()
  if(!aiming)
@@ -259,6 +265,7 @@
  aiming_time_left = aiming_time
  aiming = FALSE
  QDEL_LIST(current_tracers)
+ QDEL_NULL(trace)
  stop_zooming(user)
 
 /obj/item/gun/energy/beam_rifle/proc/set_user(mob/user)

code/modules/projectiles/projectile.dm

@@ -817,6 +817,8 @@
  RegisterSignal(src, COMSIG_ATOM_ATTACK_HAND, PROC_REF(attempt_parry))
  if(hitscan)
  process_hitscan()
+ if(QDELETED(src))
+ return
  if(!(datum_flags & DF_ISPROCESSING))
  START_PROCESSING(SSprojectiles, src)
  pixel_move(pixel_speed_multiplier, FALSE) //move it now!
@@ -911,6 +913,9 @@
  qdel(src)
  return //Kill!
  pixel_move(1, TRUE)
+ // No kevinz I do not care that this is a hitscan weapon, it is not allowed to travel 100 turfs in a tick
+ if(CHECK_TICK && QDELETED(src))
+ return
 
 /obj/projectile/proc/pixel_move(trajectory_multiplier, hitscanning = FALSE)
  if(!loc || !trajectory)