Terrain and furniture upgrades

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

Monsters can upgrade and grow into other things based on ingame elapsed time or the monsters own lifetime. Terrain and furniture are lacking that ability. This has 2-3 main usecases:

1. Making plants mutate just like monsters do. E.g entire abandoned corn fields growing into something sinister.
2. Plants growing and maturing, e.g young trees mature into grown trees given enough time.
3. Making e.g roads (well, their asphalt terrain) deteriorate over time.

Solution you would like.

I think it would be feasible to have the same approach, in terms of syntax, as monsters upgrading.

"upgrades": { "half_life": 30, "into_group": "t_region_groundcover_forest_upgrade" },

Terrain/furniture groups are a bit weird as of writing, that might be a good motivation to get those properly fixed up, too.

The big fun will probably be optimization since we have much more potentially upgradable terrain/furniture than spawned monsters.

Describe alternatives you have considered.

No response

Additional context

No response