add drop down for os

Author: Aashiq-J

ibm_catalog.json

@@ -163,7 +163,21 @@
             },
             {
               "key": "default_worker_pool_operating_system",
-              "required": true
+              "required": true,
+              "options": [
+                {
+                  "displayname": "RHEL 9",
+                  "value": "RHEL_9_64"
+                },
+                {
+                  "displayname": "Red Hat CoreOS",
+                  "value": "RHCOS"
+                },
+                {
+                  "displayname": "RHEL 8",
+                  "value": "REDHAT_8_64"
+                }
+              ]
             },
             {
               "key": "provider_visibility",