A function for conflicts on gunmods

[tenmillimaster]

Is your feature request related to a problem? Please describe.

CDDA would benefit from removing bayonets from the underbarrel slot location and adding them to their own unique slot. This presents the problem of installing a grenade launcher and a bayonet.

Solution you would like.

I would like to have gunmods be prevented from being installed if another gunmod is present. For example, certain bayonets if a grenade launcher is present. #27269 added a function that is very nearly what I'd like, which checks available slots against a list on the gunmod.

I would like a similiar function, that checks installed gunmods against a list on the gunmod.
E.g. M203 can't be co-installed with Combat knife, modified combat knife, sword bayonet... etc.
Sword bayonet can't be co-installed with m203, m320, M26, etc.

Describe alternatives you have considered.

Leaving things as is and not adding a bayonet lug location, but that means to control which guns can have bayonets and which can't we'd need, I dunno, a complex system of flags.

Additional context

I tried getting something setup for myself to being building CDDA (Codeblocks MINGW, cygwin, vsstudio) but ran into errors on each try.

I am quite inept when it comes to programming C++ (I can't even set up a build environment) but where I had intended to start was something like the below inserted at https://github.com/CleverRaven/Cataclysm-DDA/blob/master/src/item.cpp#L11262,
with a new json field other than blacklist_mod, obviously.

    for( const typeId &mod : mod.type->gunmod->blacklist_mod ) {
        if( gunmod_find().count( mod ) ) {
            return ret_val<void>::make_failure( _( "cannot be installed on a weapon with \"%s\"" ),
                                                mod.tname() );
        }
    }

[tenmillimaster]

Implemented in #69373