Allow to define sort of M2O, O2M, M2M and Reference fields when searching them
In #5853 (closed) patch we're unconditionally sorting the M2O according to the proximity field.
Not only is this behavior not efficient in all the other cases, this kind of specific order when searching on a relation is a generic feature that is useful elsewhere.
Thus adding a keyword order_search on the relational fields defining the order used when searching would be a nice addition.