Support the concept of seed hibernation

[adenitiu]

How to categorize this issue?

/area control-plane
/kind enhancement

What happened:
Apparently there is no concept of hibernation for a seed. When I hibernated a shooted seed, all pods are gone but seed care reconciler is running unaware that the shoot is hibernated and is reporting that seed conditions are not healthy.

What you expected to happen:
All conditions, shoot and seed to be healthy when the shoot is hibernated.

How to reproduce it (as minimally and precisely as possible):
Hibernate a shoot backed by a seed, aka a shooted seed.

Anything else we need to know?:

Environment:
Dev

• Gardener version: 1.90
• Kubernetes version (use kubectl version): 1.28.6
• Cloud provider or hardware configuration: all providers
• Others: