Adds back the direct link on the purchase line product's column when the
`product_matrix` is enabled. This allows the user to still click on the
product and go to its form when the module is enabled.
Also removes the direct link to the UoM, since it has no use.
Finally, sets a width for the product column in the purchase form to
keep it usable even when multiple columns are selected.
Part of task-3218314
Part-of: odoo/odoo#119381
clesgow
fcc1ad8025