Add new resource hints: max active bundles per worker

model/pipeline/src/main/proto/org/apache/beam/model/pipeline/v1/beam_runner_api.proto

@@ -2026,5 +2026,9 @@ message StandardResourceHints {
     // SDKs should accept and validate a positive integer count.
     // Payload: ASCII encoded string of the base 10 representation of an integer number of CPUs.
     CPU_COUNT = 2 [(beam_urn) = "beam:resources:cpu_count:v1"];
+    // Describes max number of active bundles per worker in transform's execution environment.
+    // SDKs should accept and validate a positive integer count.
+    // Payload: ASCII encoded string of the base 10 representation of an integer number of active bundles.
+    MAX_ACTIVE_BUNDLES_PER_WORKER = 3 [(beam_urn) = "beam:resources:max_active_bundles_per_worker:v1"];
   }
 }