Before this commit, to access the location subcontractors, you needed to search
everytime, the one2many will provide this as well as cache the result for future use.
Taskid: 2848013
Part-of: odoo/odoo#95770
Ease subcontractor stock tracking by using dedicated locations.
Simply declare location as a subcontracting one (rules are
automatically adapted) and set it on vendor.
closesodoo/odoo#88644
Task: 2720393
Related: odoo/upgrade#3755
Signed-off-by: Tiffany Chang <tic@odoo.com>