Show all roles in user list table

[scribu]

From [22686]:

we should show a comma-separated list of all roles, editable or otherwise, and this list should be filterable, either by user, or by the roles which can appear. Probably both.

Previously: #22361

Where should filtering be added, and to what end? If we're expected to find existing elements in the array, perhaps it should be filtered pre-translation. If not, this at least gives an opportunity to add elements.

Before: return implode( ', ', $role_str );

After: return implode( ', ', apply_filters( 'wp_user_list_get_role_str', $role_str, $user_object ) );

If the intention was to modify the column's output after the implode(), another filter would be necessary.

I know this ticket is now for a future release. I'm still interested in the inclusion of filtering of the roles, pre-translation. Am I the only one, or should I submit a patch to that effect?