[IMP] web: support oe_read_only and oe_edit_only in x2m list

Before this rev., classNames 'oe_read_only' (only display in
readonly mode) and 'oe_edit_only' (only display in edit mode)
didn't work in x2m lists inside form views (only the cells in the
tbody were hidden, but not the header). This rev. makes this work.

Task 1949618

closes odoo/odoo#36117

Signed-off-by: Aaron Bohy (aab) <aab@odoo.com>