[Placement Group] Capture Child Task Part 1 (#10968)

* In progress.

* In progers.

* Done.

* Addressed code review.

* Increase timeout to make a test less flaky.

* Addressed code review.

* Addressed code review.

python/ray/state.py

@@ -6,6 +6,7 @@ import time
 
 import ray
 
+from google.protobuf.json_format import MessageToDict
 from ray import (
     gcs_utils,
     services,
@@ -423,7 +424,10 @@ class GlobalState:
                 placement_group_info.placement_group_id),
             "name": placement_group_info.name,
             "bundles": {
-                bundle.bundle_id.bundle_index: bundle.unit_resources
+                # The value here is needs to be dictionarified
+                # otherwise, the payload becomes unserializable.
+                bundle.bundle_id.bundle_index:
+                MessageToDict(bundle)["unitResources"]
                 for bundle in placement_group_info.bundles
             },
             "strategy": get_strategy(placement_group_info.strategy),