When we convert Bootstrap grids to tables for e-mail compatibility, we
need to complete rows whose column sizes don't add up to 12. The way it
was, the last column was stretched to fill up the row, which is wrong as
it can affect the width of its contents.
With this commit, a new, empty column is appended to the row to fill it
up without affecting the existing rows. This is a more accurate way to
emulate the behavior of Flexbox.
task-2936705
X-original-commit: 462b698732dbc0e71972ddbe86c687f4bb3f9492
Part-of: odoo/odoo#97962
Antoine Guenet
4897f23296