[FEAT] Add host uptime to observed host object

[brooksmtownsend]

Right now, the event processor uses the timestamp of the first host heartbeat to record the first_seen value of a host. This can differ wildly depending on when the host started and when the lattice observer discovered it. In addition to tracking these values, it would be valuable to know the absolute uptime for the host.

This will also require adding the uptime to the host heartbeat in the wasmcloud-otp repo.

References

• Using timestamp: https://github.com/wasmCloud/lattice-observer/blob/723fb0dfb57ba5aa831d8663ebd8df43cffd4e08/lib/lattice_observer/observed/lattice.ex#L132
• control interface uptime: https://github.com/wasmCloud/wasmcloud-otp/blob/main/host_core/lib/host_core/control_interface/server.ex#L31-L37

(cc @autodidaddict for thoughts)

[connorsmith256]

Resolved by https://github.com/wasmCloud/lattice-observer/pull/29