Figure out a way to print names of intersecting messages in const context.

[jawoznia]

Currently in verify_no_collissions we will call
panic!("Message overlaps between interface and contract impl!");
in case of intersection between two or more messages. This is not helpful enough and it would be best to print duplicated messages name.

Unfortunately because it all happens in const fn we can't just call format! and concatenate two strings.

Below example compiles and could be a way to workaround this.
panic!("{}", msgs[i][outer_i]);
Maybe there is a way to print message before panicking explaining what is causing compilation to fail.

[jawoznia]

This is a follow up issue to #8