Add new strategy: remove a channel to a node, if the node was not seen for X amount of time

[mjadach-iv]

Is your feature related to a problem?

HOPRd is not closing channels to nodes that it doesn't see on the network and doesn't have in the local node database.

Describe the feature you'd like

The strategy would accept time like '5m', '24h', '30d'.
It should close channels if a node was not seen by our node in that specified time.

If a node is present on the node database, then we can use lastSeen for that information.
If the node database is removed or a node is not present in that db, then we should take into account node uptime as a counter since when the nodes on the network are offline.

[NumberFour8]

If the node database is removed or a node is not present in that db, then we should take into account node uptime as a counter since when the nodes on the network are offline.

As mentioned in the meeting, this part would be ineffective for those that restart their node from time to time (e.g. due to updating).

The situation where a node is not in the DB is an edge-case IMHO, since it is the result of DB deletion in our staging environment.
For nodes that are in the DB, this is a non-issue, since such node already has some quality (which would be low if the last seen value is old), and the standard algorithm of Promiscuous strategy will apply.