Add sorting for some Orders search results list columns

Overview: Split from UIOR-269 to unblock that story. This story describes columns in the PO search results that should be sortable ascending and descending.

Scenarios

1. Scenario 1
   • Given the PO search results list
   • When a user views the PO search results list
   • Then the user should be able to sort the results list ascending and descending by clicking on any of the column headers. Some sorting was previously enabled in UIOR-269 (for PO number, Status, Order type, and Last updated columns). Add sorting for the following column headers, including the up/down arrows indicating sort order:
     • Vendor
     • Acquisitions unit (DB: Must be split out into separate issue)
     • Assigned to
   • And the default sort order should remain descending by PO number (numerics descending, then alphas descending)
2. Scenario 2
   • Ensure automated testing coverage for this new code is 80% plus and confirm with screenshot

NOTE: Per aliaksei_chumakou The back-end can't sort on some columns, like Vendor, Acquisitions unit, Assigned to. They're uuids comes from back-end. Let's move to separate ticket.