When removing an item in x2many fields from the res.config.settings form, the
client interprets it as a set of link commands for the remaining items, as a
result, the items that should have been removed are not removed.
This generalizes the fix made for the splash screen images in pos_self_order by
which this issue was first observed.
The test is also moved to the point_of_sale module as it is not specific to
pos_self_order. Also note that the test is manually doing what is observed from
the client.
closesodoo/odoo#143165
Signed-off-by: Adrien Guilliams (adgu) <adgu@odoo.com>