This UI enables the user to set can_manage_group setting to a
combination of users and groups, replacing the old dropdown UI
which just allowed setting user to a single system group.
Fixes part of #28808.
This commit adds a group level setting can_manage_group in
`#groups` overlay. This setting can be set while creating a
new user_group and can be changed for existing groups.
This commit updates the dropdown menu width to be set such that
the menu is wide enough to have options in a single line.
This change is only for group-based setting dropdowns in
organization, stream and group settigs.
Fixes#30673.
Instead of having different functions to set values of dropdown widget
variables, we now use a single function to set their values by passing
the setting name to the function.