[Feat]: better offline detectability

[pwltr]

Problem or use case

NWPathMonitor can sometimes provide a false positive for the offline state, for example with Network Link Conditioner set to 100% loss it still reports as "online".

Proposed solution

Instead of relying on NWPathMonitor only we could send requests to various endpoints. If all of them fail, consider the device offline.

Alternatives considered

No response

Additional context

see #528