Add explicit "roofs" to the nether monster corpse

[PatrikLundell]

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

I'm in the process of adding explicit roofs to mapgen in order to eventually be able to remove the reliance of add_roofs to provide these (add_roofs has negative side effects, such as plugging holes in collapsed towers, etc.).

However, I failed at doing this to the monster corpse due to an inability to understand how to add the "roofs" into the complex structure. Hence, I ask for someone who is capable of doing to to perform that task.

Solution you would like.

Define "roof" components for the two above ground sections of the monster corpse and integrate those into the structure.

Describe alternatives you have considered.

No response

Additional context

No response

[PatrikLundell]

Fixed by #74792.