User Autocomplete Dropdown Fails to Prioritize Target Usernames, Limiting Role Assignment

Description:

Username autocomplete functionality in the "Add Roles to User" menu is inefficient. When trying to add roles to a user by searching for their username, the current setup fills the autocomplete dropdown based on alphabetical sorting without considering if the username starts with the search term. This results in a cumbersome experience, especially since the dropdown is limited to 10 items.

Steps to reproduce:

Open the "Add Roles to User" menu.
Start typing a username you intend to assign a role to.
Observe the items that appear in the autocomplete dropdown.
Expected behavior:
The dropdown should prioritize usernames that start with the search term for quicker and more efficient role assignment.

Start from the “Add Roles to User” menu and reproduce the username search described in the issue, checking how the autocomplete results are ordered and limited to 10 items. Done means usernames beginning with the search term are prioritized in the dropdown, while role assignment continues to work.