Simplify the user deletion "Attribute all content" flow

[ashwin.parthasarathi]

When deleting a user and trying to "Attribute all content to" to another user,

1. If the user list is very long, it is very difficult to search for specific users.
2. There is no indication of the role of the user, hence that too makes the process difficult.

Possible solutions are,

1. Using Select2 with text search
2. Add opt-group to divide users based on the Roles

[ashwin.parthasarathi]

Admin view of the user deletion process with the dropdown in point marked