[IMP] account_intrastat:fields in grouped aml view

This commit refactors the protected fields out of the hardcoded list in
the account_move_line model, and into a function that can be overriden
in inherited models.

This allows for account_intrastat to specify that the intrastat
transaction code field and the intrastat product origin country field
should not be editable after the accounting lock date.

(In the corresponding commit these intrastat fields are added to the
journal views)

related PR: https://github.com/odoo/enterprise/pull/27049



closes odoo/odoo#91134

Task-id: 2753542
Related: odoo/enterprise#27049
Signed-off-by: William André (wan) <wan@odoo.com>