Initial WS2P connection is too slow

In the very first phase of WS2P connection when we start the service (startCrawling()), we try each peer one by one and most of the time without success. This delays a lot the start of the whole node's lifecycle (pull the network, ask for missing blocks, getting new peers, etc.). This is quite annoying.

Instead of connecting node by node, I suggest we try a bunch of nodes at once and then repeat the process. For example, we could try 10 peers in a row, then 10 other peers, etc.