[PlacementGroup]Add PlacementGroup wait java api (#12499)

* add part code

* add part code

* add part code

* add part code

* fix review comments

* fix compile bug

* fix compile bug

* fix review comments

* fix review comments

* fix code style

* add part code

* fix review comments

* fix review comments

* fix code style

* rebase master

* fix bug

* fix lint error

* fix compile bug

* fix newline issue

Co-authored-by: 灵洵 <fengbin.ffb@antgroup.com>

java/api/src/main/java/io/ray/api/runtime/RayRuntime.java

@@ -221,4 +221,12 @@ public interface RayRuntime {
    * @param id Id of the placement group.
    */
   void removePlacementGroup(PlacementGroupId id);
+
+  /**
+   * Wait for the placement group to be ready within the specified time.
+   * @param id Id of placement group.
+   * @param timeoutMs Timeout in milliseconds.
+   * @return True if the placement group is created. False otherwise.
+   */
+  boolean waitPlacementGroupReady(PlacementGroupId id, int timeoutMs);
 }