[IMP] web: add BadgeField component

This new field component displays the field's value inside a
bootstrap pill badge. Supported field types are 'char', 'selection'
and 'many2one'. The background color of the badge can be customized
by using the decoration-xxx mechanism, e.g.
 <field name="state" decoration-danger="state == 'cancel'" widget="badge"/>

Part of task 2195254