New "conflicts" property for .info.yml extension files

The main question here is what's the action expected when a conflict is found. Depending on what we want the action to be, just by using hook_requirements() we might be ok.

You absolutely can do this with hook_requirements, the plan is to replace the conflicts piece with info yaml or composer.json

So far, we have hook_requirements() - which can be bypassed if you use -y in drush, and composer's which may or may not be used for custom modules. My question remains: let's say we have a conflict in *.info.yml; is it there for informational reasons or should it 100% prohibit the coexistence of the module without any bypass?

I think it should stop the operation entirely.

Also, adding 'for information purpose' now seems pointless since it'll probably be just taken it out later, saying it's not needed.

Cheers,
Beautifulmind