Before this commit, the kanban view has a `className` getter to easily
add a class if needed. The list view only uses the className given in
the props and so className is added in the view.
This commit adds a className getter to be consistent with kanban view
and to allow to easily add a className to a specific case (that is for
an eventual customization).
task-2713538
Part-of: odoo/odoo#98380
Xavier BOL (xbo)
15f2d75bdb