Implement widget definition API to fetch allowed statuses

1. work item type widget definition on different levels. Here we'll list all available statuses for the given work item type and the top level namespace (group). Depending on the setting on namespace to use custom status or system defined status, we'll chose a different set of statuses in iteration 2
   1. namespace
   2. project
   3. group

See the MR that introduced the mock API for example and the POC that implements these APIs

In iteration 1 we only want to return the statuses of the system defined lifecycle that matches the work item type.