Add indices:data/read/search* to ml_full_access for Agentic Search

QueryPlanningTool samples documents from the target index using a
matchAllQuery search. This requires indices:data/read/search* permission
which is consistent with other full_access roles (anomaly_full_access,
ppl_full_access, asynchronous_search_full_access, forecast_full_access).

Signed-off-by: Owais Kazi <owaiskazi19@gmail.com>

Author: owaiskazi19

config/roles.yml

@@ -333,6 +333,7 @@ ml_full_access:
         - '*'
       allowed_actions:
         - 'indices:admin/mappings/get'
+        - 'indices:data/read/search*'
         - 'indices_monitor'
 
 # Allows users to use all Notifications functionality