[enh] #1325 Spread events about synchronization for better reporting

app/modules/crawler/lib/sync.ts

app/modules/crawler/lib/sync/BMARemoteContacter.ts

app/modules/crawler/lib/sync/IRemoteContacter.ts

app/modules/crawler/lib/sync/P2PSyncDownloader.ts

app/modules/crawler/lib/sync/WS2PRemoteContacter.ts

app/modules/crawler/lib/sync/Watcher.ts

app/modules/crawler/lib/sync/p2p/p2p-candidate.ts

app/modules/crawler/lib/sync/v2/DownloadStream.ts

app/modules/ws2p/lib/WS2PDocpoolPuller.ts