feat: allow connectors to return an arbitrary amount of nodes and edges

[pekasen]

Problem: Connectors may return information on one node and multiple edges. This is derived from the original use case of sampling Telegram channels, where we would receive multiple shares but only information on the currently visited channel. For other use cases this behavior is counter-productive. E.g., Twitter's friends and followers endpoints (Version 2) return node information for each friend/follower encoded in the edge information.

Solution: It should do not take changes in the current architecture to allow multiple node returns, as the status of each node is encoded in a separate task table, unlike before where tracking tasks was done implicitly and a node already being present in the node table prevent the scraper so visit that node.