[feature] allow configuring automatic disconnected machine eviction rules in Omni

[Unix4ever]

Goal

Disconnected machines should be replaced by the healthy ones in the machine class managed machine sets.
Disconnected machines should not block the cluster deletion.

Solution

The rule should be flexible enough to allow the user to set the conditions and timeouts for automatic disconnected node removal.

Can probably use some expression language for that.

[smira]

I would probably make it more generic, by saying that configuring some rules for "unhealthy" in general machines to be replaced (including disconnected).