Feat: added a sendqueue to the gossip module

plugins/autopeering/plugin.go

plugins/gossip/events.go

plugins/gossip/neighbors.go

plugins/gossip/plugin.go

plugins/gossip/protocol.go

plugins/gossip/protocol_v1.go

plugins/gossip/send_queue.go

plugins/gossip/server.go

plugins/gossip/transaction_processor.go