Give only weapons normally available on the map in CA/LMS/FT

My reasoning is that it'll introduce more variety to gameplay. No more vortex camping in LMS on warfare/darkzone, no more infite electro spam in CA on finalrage, etc. It's optional using server cvars since some people will no doubt hate it (even more so if they find out it's my idea) but by default players will only spawn with available weapons, otherwise nobody would even try it.

The implementation feels a bit messy, not sure if this is the best way. Explanation in LMS code. I tried a few combinations of rulesets, mutators and modes and nothing obvious was broken but the multiple layers of overriding don't make it easy to feel confident.

Also not sure if it's safe to return early from MUTATOR_HOOKFUNCTIONs since they're implemented using [[accumulate]]. If so, we could reduce nesting in some cases.