We move the function loadFields from the view service to a newly created
field service. That service can also be used to load model fields for a
given path (loadPath), i.e. load all model fields for the models
traversed by the given path.
We use loadPath in useModelField and DomainSelector.
closesodoo/odoo#117882
Related: odoo/enterprise#39418
Signed-off-by: Aaron Bohy (aab) <aab@odoo.com>