core, ethdb, metrics, p2p: expose various counter metrics for grafana

p2p/server.go

@@ -685,9 +685,8 @@ running:
 			// This channel is used by RemoveTrustedPeer to remove an enode
 			// from the trusted node set.
 			srv.log.Trace("Removing trusted node", "node", n)
-			if _, ok := trusted[n.ID()]; ok {
-				delete(trusted, n.ID())
-			}
+			delete(trusted, n.ID())
+
 			// Unmark any already-connected peer as trusted
 			if p, ok := peers[n.ID()]; ok {
 				p.rw.set(trustedConn, false)