SWIM - An additional option to set a starter list of nodes to avoid multicast

[zarusz]

Currently, when a Node joins it multicast the join to let other members it had joined.
Other members then send a welcome message with the current list of members, so that the Node can catch up on the cluster membership fast.

However, we could also provide an option where the initial list of few members is provided upfront as a configuration (bootstrap node list). This could work in some scenarios and thus we could avoid the reliance on the multicast for the initial discovery.