[Java] Load driver resources from local path. (#3001)

## What do these changes do?
1. Add a configuration item `driver.resource-path`.
2. Load driver resources from the local path which is specified in the `ray.conf`.

Before this change, we should add all driver resources(like user's jar package, dependencies package and config files) into `classpath`.

After this change, we should add the driver resources into the mount path which we can configure it in `ray.conf`, and we shouldn't configure `classpath` for driver resources any more.

## Related issue number
N/A

java/runtime/src/main/resources/ray.default.conf

@@ -25,9 +25,15 @@ ray {
   // Available resources on this node, for example "CPU:4,GPU:0".
   resources: ""
 
-  // If worker.mode is DRIVER, specify the driver id.
-  // If not provided, a random id will be used.
-  driver.id: ""
+    // Configuration items about driver.
+    driver {
+      // If worker.mode is DRIVER, specify the driver id.
+      // If not provided, a random id will be used.
+      id: ""
+      // If worker.mode is WORKER, it means that worker will load
+      // the resources from this path to execute tasks.
+      resource-path: /tmp/ray/driver/resource
+    }
 
   // Root dir of log files.
   log-dir: /tmp/ray/logs
@@ -76,4 +82,5 @@ ray {
     // RPC socket name of Raylet
     socket-name: /tmp/ray/sockets/raylet
   }
+
 }