Bring back medibot chemicals

[Capsandi]

Prior to https://github.com/tgstation/tgstation/pull/45953, medibots used chemicals to heal (apparently they also had some sort of virus curing function, but I never saw it used). They also had a slot for beakers so that anyone with MD/robotics access (or an emag) could override the basic brute/burn healing chem with more helpful medicines or any sort of toxin. This change was made midway through cobby's medical overhaul to nerf medibots from being "reliable free healing", except that's what they became and still are. Now medibots heal brute from near crit until your almost perfectly fine, and thats just the basic bots. They are never a risk unless someone buys an emag, and even then they do brute damage while injecting chloral, so it gets smashed by everyone but AFKs
Medibots were the most reliable way to poison indiscriminately. Every other method can be ran away from (smoke, foam), requires a reagent gun and being chased by a very angry spaceman (just use a gun), or praying that the station runs out of donuts, so they eat the chef's poisoned food. If there was an issue with the synth chems they can be nerfed alone but medibots now are just free healing with 0 risk.

[CPTANT]

Yeah that PR basically did the reverse of what it claimed to do.....

I really miss the abillity to poison this way, both as traitor and also as rogue ai.