refactor: move column cache reset from setNewConnection to tryConnect

The reset belongs in tryConnect() because that is the earliest point where
we have a new connection but have not yet issued any system table queries.
By the time setNewConnection() is called, tryConnect() has already reset
the caches and populated them via refreshNodeListAndTokenMap() — so resetting
in setNewConnection() was discarding freshly-discovered, correct, warm caches
and forcing an unnecessary extra SELECT * on the next query.

Both connect() and backgroundReconnect() go through tryConnect() before
setNewConnection(), so a single reset in tryConnect() covers both flows.

Author: nikagra

driver-core/src/main/java/com/datastax/driver/core/ControlConnection.java

@@ -340,11 +340,6 @@ private void signalError() {
   private void setNewConnection(Connection newConnection) {
     Host.statesLogger.debug("[Control connection] established to {}", newConnection.endPoint);
     newConnection.setOwner(this);
-    // Reset column caches so the new connection triggers a fresh SELECT * to discover which
-    // columns the server exposes before switching to projected queries.
-    localColumns = null;
-    peersColumns = null;
-    peersV2Columns = null;
     Connection old = connectionRef.getAndSet(newConnection);
     if (old != null && !old.isClosed()) old.closeAsync().force();
   }
@@ -438,9 +433,9 @@ private Connection tryConnect(Host host, boolean isInitialConnection)
       connection.write(new Requests.Register(evs));
 
       // Reset column caches so refreshNodeListAndTokenMap() uses SELECT * to rediscover
-      // which columns this server exposes, rather than a projected query built for the
-      // previous connection's server. setNewConnection() also resets these, but it is
-      // called after tryConnect() returns — too late to protect the queries below.
+      // which columns this server exposes, rather than a projected query built for a
+      // previous connection's server. The caches are populated during the queries below
+      // and remain warm for the lifetime of this connection.
       localColumns = null;
       peersColumns = null;
       peersV2Columns = null;