[IMP] lead: improve extensibility of partner create method
[IMP] lead: improve extensibility of partner create method

Before this commit _lead_create_contact actually constructed values AND
created the partner in one single step, making it difficult to override
in localizations that affect the partner model.

As containing method already existed, the partner creation was moved up
to this method, and the method was renamed to match with the file's
conventions. Now this method cleanly constructs the values.

Closes #16493 .

ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo