Fix zone rotation in faction camp farms

[eltank]

Summary

Bugfixes "Fix zone rotation in faction camp farms"

Purpose of change

Fixes #51459 - player-defined zones in basecamp farm OMTs get rotated when interacting with the bulletin board.

Describe the solution

Avoid calling map::generate on the tinymap loaded from the farm OMT. Use fake_map instead and call mapgen directly, using mapgendata extracted from the farm OMT.
Refactor fake_map to make it easier to use (no-arg constructor, hardcoded z-level).
Revert the no_rotate_npcs workaround from #47730.

Describe alternatives you've considered

Implement something similar to get_changed_ids_from_update() (mapgen.cpp) that runs mapgen in a fake_map and returns terrain/furniture data in std::map format.

Refactor mapgen code to not rotate maps, but rather transform the coordinates of the json template before applying modifications to the map. I think bugs of this nature will continue to crop up until this is done.

Testing

Load the save from the bug. Inspect the bulletin board. Open zone manager and check that zones have not moved. Also the follower NPCs are still in the same places.

Build a field base camp with a farm, plow and plant seeds from the camp menu.

Additional context

While testing I discovered that the "type 2" farm for the field base camp is broken (missing the "farming" capability) so I'll fix that in another PR.