Prior to this commit the 'disabled' state (eg. studio icon in a
not-editable view) and the 'no-notification' state (eg. messaging icon
without badge) shared the same design.
While the disabled state should be used for not-clickable elements only,
available systray items should always appear clickable, even
when there are no new notifications.
This commit moves the `o_disabled` class outside the burger_menu
component, making it generic and available for other components too.
Systray items without notification are now styled normally.
The simple presence of the badge communicates the user that a new
notification has been sent.
This commit is part of v16 overall restyle (task-2704984).
task-2712151
Part-of: odoo/odoo#82434
stefanorigano (SRI)
ad64f56f6f