Fixed grenade casing name not changing

Fixed grenade casing not being renamed to grenade when complete and made all assembly messages refer to the assembly as "grenade assembly" and "large grenade assembly".

- The grenade assembly is called "grenade casing" before anything is done (like it always was)
- The grenade assembly is called "unsecured grenade" when a activation mechanism is added (like before https://github.com/tgstation/-tg-station/commit/f645037dd5ffe491c94f73a39b3aac312e51d579)
- The grenade assembly is called "grenade" when finished (like before  https://github.com/tgstation/-tg-station/commit/f645037dd5ffe491c94f73a39b3aac312e51d579)
- Renamed large chem grenade to "large grenade"
- Made using a wrench on a unsecured grenade remove the payload on the first use, and the activation mechanism on the second use (because we don't want to always remove both at the same time)
- Made cable_coil drop on the floor if it was used as activation mechanism

Fixes https://github.com/tgstation/-tg-station/issues/2378