allowCrossProject for _search (#136397)

Author: piergm

server/src/main/java/org/elasticsearch/action/search/SearchRequest.java

@@ -162,6 +162,11 @@ public boolean allowsRemoteIndices() {
         return true;
     }
 
+    @Override
+    public boolean allowsCrossProject() {
+        return true;
+    }
+
     /**
      * Creates a new sub-search request starting from the original search request that is provided.
      * For internal use only, allows to fork a search request into multiple search requests that will be executed independently.