Move PeerFinder's logger to the expected package (#39412)

Today the abstract `org.elasticsearch.discovery.PeerFinder` uses the logger of
its implementation, which in production is in `o.e.cluster.coordination`. This
turns out to be confusing and unhelpful, so with this change we move to using
the logger that belongs to `PeerFinder`.

server/src/main/java/org/elasticsearch/discovery/PeerFinder.java

@@ -69,7 +69,7 @@
 
 public abstract class PeerFinder {
 
-    protected final Logger logger = LogManager.getLogger(getClass());
+    private static final Logger logger = LogManager.getLogger(PeerFinder.class);
 
     public static final String REQUEST_PEERS_ACTION_NAME = "internal:discovery/request_peers";