Add looks_like to vanilla guns

[ghost]

Summary

SUMMARY: Infrastructure "Add looks_like to all vanilla guns"

Purpose of change

Start of .json work to complete #34230.

Describe the solution

Adds looks_like to all vanilla guns according to this whitelist(can't use abstracts as pointed out by anothersimulacrum):
Pistol: Glock 17
Revolver: S&W 619
Shotgun: Remington 870
SMG: H&K MP5
Rifle: AR-15
Launcher: M79
Crossbow: Crossbow(duh)
Sling/slingshots: Slingshot
Bow: Longbow

Describe alternatives you've considered

1. Compressing pistol & revolver backups into Glock 17 for both.
2. M134D-H Minigun as backup for turret guns + M/HMGs.
3. M14 as backup for wood stock rifles & sniper rifles.

Testing

Hodor's Tileset:
Brace slingshot, sling, & slingshot top-to-bottom before looks_like(Brace has no texture, slingshot & sling do):

After, showing looks_like works & doesn't override existing textures:

Additional context

Future PRs will be in categories of items in vanilla before moving onto mods. Planning on food or vehicle parts next.