Projectile Subsystem and misc adjustments

[fira]

About The Pull Request

What this does:

• Adds a projectile subsystem for scheduling their movement. The follow_flightpath sleeps are detrimental to perf, and instead this allows them to be updated 2x as often.
• Projectile speed is +-15% and has a firing offset, to result in a proper bullet trail instead of a dotted line.
• Gun projectile firing angle takes into account scatter and clicked pixel. This is mostly a visual change, but also affects direction bullets take past initially aimed point.
• Decouples gun/projectile from sleeps. This has caused many practical issues in the past.
• Removes simple_mobs firing and AMMO_SCANS_NEARBY. They're defunct/broken.
• Removes projectile speed-up from AMMO_ROCKET - instead granting them full speed. This only really mattered for thermobaric launcher at long range.

Why It's Good For The Game

Smoother, more visual feedback (perhaps to a fault, as it shows how goofy our system is)

Example of in-turf targeting, two trajectories based on clicking either X mark:

Video example of difference, yes, it is subtle:
https://streamable.com/ph18yj
https://streamable.com/ndq7f5

Changelog

🆑
add: Added +-15% variation to bullet speed and firing offsets to result in a better bullet trail.
add: Gun firing now takes into account click position. This can bend the bullet trajectory beyond the clicked point.
add: Projectiles now attempt to mimick a proper bullet stream by offsetting slightly. This is purely visual.
code: Removed rocket speed-up, and gave them full speed. Only really matters for offscreen admin-spawned thermobaric rockets.
fix: Fixed deletion issues with projectiles, and decoupled it from gun logic due to recurring issues.
del: Removed simple_mob-s shooting and AMMO_SCANS_NEARY. They're defunct/broken.
fix: Removed a number of micro sleeps in explosion code. This may reduce amount of shrapnel hits.
code: Tweaked Aimed Shot homing logic which should make it even more accurate in the offchance it ever matters.
/:cl:

[hry-gh]

this certainly looks good for a TM - i'm sure there's edge cases that i can't predict rn that'll come up then

[fira]

Rocket speedup was super painful and unreliable to deal with when it came to variable speed and travel carryover so i just removed it entirely, giving them full speed all the time instead...

This impacts two situations:

• It makes the RPG hit more reliably and slightly faster beyond PB range (max 15-20%) which should fall back in line with people expectations from before
• It makes admin-spawned thermobaric launcher faster without having to fire offscreen for it, but that's basically never used

[fira]

The sleep safety net isn't good enough, causing erroring bullets to be stuck in midair. This is a problem because it appears we still have sleeps in /mob/living/bullet_act somehow (i suspect heavily /mob/living/carbon/Xenomorph/apply_damage)

[hry-gh]

code quality lgtm, still possible there's something being overlooked, but

[ghost]

Code LGTM. Testmerges went well.