[IMP] various: optimize _name_search

In the overrides of _name_search we should avoid creating domains with
huge lists of ids as it is inefficient.
We can also make sure that we optimize the empty search as in this case
the custom domain doesn't make sense, we can simply search on an empty
domain and, thanks to the limit argument, still keep a fast query.

Linked to task 1918906

Thanks to @odony and @nseinlet

closes odoo/odoo#30155

closes odoo/odoo#30887