[Feature]: Check instance health via cloud provider API

[Egor-S]

Problem

Interrupted instances (spot or removed from outside of dstack) are shown as idle for a long time

Solution

If the shim doesn't respond, ask the backend about the instance existence

Benefit

Do not waste resources on pinging or trying to use dead instances

Alternatives

Decrease the termination period for unresponsive and non-occupied instances

Would you like to help contributing this feature?

Yes