fix: init last access timestamp of nodes to current time

- Initialize every node's last access timestamp to the current time to
avoid null referencing when checking for healthcheck due status

Author: tharropoulos

src/main/java/org/typesense/resources/Node.java

@@ -25,6 +25,7 @@ public Node(String protocol, String host, String port) {
         this.host = host;
         this.port = port;
         this.isHealthy = true;
+        this.lastAccessTimestamp = LocalDateTime.now();
 
         if (protocol == null) {
             throw new RuntimeException("Protocol cannot be null");