nSyncStarted, mapBlockSource, g_outbound_peers_with_protect_from_disconnect were all only used by PeerManagerImpl methods already.
This is a backport of [[https://github.com/bitcoin/bitcoin/pull/20942 | core#20942]] [1/9]
https://github.com/bitcoin/bitcoin/pull/20942/commits/9781c08a33569370f191b30cc7e2ce9b5317eb3e