Use singe list of `cards:` per room in `lovelace_rooms.yaml`

[tbrasser]

I used to have separate lists for plants, lights and devices, and then separate entries for media and other things. Refactoring this to a single cards: list.

• [x] lovelace/.cards/plants.yaml
• [x] lovalace/.cards/lights.yaml
• [x] lovelace/0_main.yaml
• [x] lovelace/rooms.yaml
• [ ] lovelace/views.yaml
• [ ] lovelace/.cards/security.yaml
• [x] lovelace/.cards/devices.yaml