Use `load` rather than `require` for factories
Use `load` rather than `require` for factories

When using factory_girl_rails and spring on an application, I found that none of the spree-provided factories were available to me. Using them when running the tests with spring resulted in `Factory Not Registered` errors. The factories work fine without spring.

This seems to do with the factory_girl_rails initializer, which reloads all factories after spring forks. `require` happens only once, so when factory_girl reloads the factories it no longer sees the spree factories I have required.

In my app, I changed `require "spree/testing_support/factories` to `load "spree/testing_support/factories.rb`, which will load each time that initializer is run. However, spree itself needs to `load` rather than `require` the individual factory files.

Fixes #6534

siddharth28/spree,trigrass2/spree,pervino/spree,locomotivapro/spree,AgilTec/spree,SadTreeFriends/spree,alejandromangione/spree,jimblesm/spree,shaywood2/spree,APohio/spree,karlitxo/spree,edgward/spree,cutefrank/spree,karlitxo/spree,vinayvinsol/spree,tancnle/spree,zamiang/spree,softr8/spree,shaywood2/spree,pulkit21/spree,reidblomquist/spree,ayb/spree,alvinjean/spree,locomotivapro/spree,priyank-gupta/spree,sliaquat/spree,dafontaine/spree,shaywood2/spree,beni55/spree,abhishekjain16/spree,rajeevriitm/spree,calvinl/spree,ramkumar-kr/spree,brchristian/spree,zaeznet/spree,joanblake/spree,JDutil/spree,quentinuys/spree,azranel/spree,JDutil/spree,TimurTarasenko/spree,imella/spree,gautamsawhney/spree,NerdsvilleCEO/spree,jaspreet21anand/spree,jeffboulet/spree,yushine/spree,grzlus/spree,welitonfreitas/spree,piousbox/spree,odk211/spree,ahmetabdi/spree,mleglise/spree,hifly/spree,DynamoMTL/spree,brchristian/spree,omarsar/spree,ramkumar-kr/spree,reidblomquist/spree,dafontaine/spree,vmatekole/spree,abhishekjain16/spree,lyzxsc/spree,tomash/spree,siddharth28/spree,vcavallo/spree,patdec/spree,firman/spree,imella/spree,mindvolt/spree,yiqing95/spree,KMikhaylovCTG/spree,jasonfb/spree,TimurTarasenko/spree,omarsar/spree,lyzxsc/spree,hifly/spree,tomash/spree,jasonfb/spree,JuandGirald/spree,groundctrl/spree,maybii/spree,orenf/spree,wolfieorama/spree,pulkit21/spree,rajeevriitm/spree,orenf/spree,berkes/spree,kewaunited/spree,sfcgeorge/spree,JuandGirald/spree,sliaquat/spree,jimblesm/spree,hoanghiep90/spree,caiqinghua/spree,gregoryrikson/spree-sample,brchristian/spree,CJMrozek/spree,shekibobo/spree,azranel/spree,SadTreeFriends/spree,TrialGuides/spree,softr8/spree,shekibobo/spree,caiqinghua/spree,wolfieorama/spree,gautamsawhney/spree,thogg4/spree,caiqinghua/spree,piousbox/spree,ramkumar-kr/spree,mleglise/spree,pulkit21/spree,robodisco/spree,lsirivong/spree,jeffboulet/spree,Hawaiideveloper/shoppingcart,pervino/spree,progsri/spree,lyzxsc/spree,priyank-gupta/spree,KMikhaylovCTG/spree,berkes/spree,ahmetabdi/spree,grzlus/spree,siddharth28/spree,jaspreet21anand/spree,TrialGuides/spree,KMikhaylovCTG/spree,yiqing95/spree,tancnle/spree,raow/spree,groundctrl/spree,Lostmyname/spree,grzlus/spree,hifly/spree,maybii/spree,piousbox/spree,jparr/spree,karlitxo/spree,kewaunited/spree,vcavallo/spree,quentinuys/spree,Hawaiideveloper/shoppingcart,vinayvinsol/spree,imella/spree,reidblomquist/spree,Kagetsuki/spree,moneyspyder/spree,tomash/spree,NerdsvilleCEO/spree,zamiang/spree,ayb/spree,mindvolt/spree,JDutil/spree,miyazawatomoka/spree,welitonfreitas/spree,karlitxo/spree,CiscoCloud/spree,njerrywerry/spree,hoanghiep90/spree,mindvolt/spree,DarkoP/spree,trigrass2/spree,Lostmyname/spree,miyazawatomoka/spree,lsirivong/spree,joanblake/spree,caiqinghua/spree,vmatekole/spree,SadTreeFriends/spree,Kagetsuki/spree,DynamoMTL/spree,shekibobo/spree,njerrywerry/spree,jparr/spree,orenf/spree,rakibulislam/spree,beni55/spree,abhishekjain16/spree,sliaquat/spree,SadTreeFriends/spree,sliaquat/spree,thogg4/spree,tancnle/spree,kewaunited/spree,locomotivapro/spree,lsirivong/spree,alejandromangione/spree,shekibobo/spree,patdec/spree,alvinjean/spree,DynamoMTL/spree,DynamoMTL/spree,CJMrozek/spree,quentinuys/spree,orenf/spree,moneyspyder/spree,groundctrl/spree,dafontaine/spree,patdec/spree,raow/spree,edgward/spree,progsri/spree,priyank-gupta/spree,zaeznet/spree,moneyspyder/spree,shaywood2/spree,beni55/spree,volpejoaquin/spree,FadliKun/spree,mindvolt/spree,FadliKun/spree,brchristian/spree,fahidnasir/spree,miyazawatomoka/spree,gautamsawhney/spree,TrialGuides/spree,miyazawatomoka/spree,beni55/spree,TimurTarasenko/spree,patdec/spree,cutefrank/spree,njerrywerry/spree,useiichi/spree,mleglise/spree,pervino/spree,thogg4/spree,gautamsawhney/spree,rakibulislam/spree,thogg4/spree,hifly/spree,JuandGirald/spree,AgilTec/spree,vcavallo/spree,Kagetsuki/spree,robodisco/spree,vcavallo/spree,vinsol/spree,moneyspyder/spree,progsri/spree,zamiang/spree,trigrass2/spree,softr8/spree,DarkoP/spree,volpejoaquin/spree,omarsar/spree,alejandromangione/spree,CJMrozek/spree,rajeevriitm/spree,ayb/spree,DarkoP/spree,useiichi/spree,APohio/spree,zaeznet/spree,FadliKun/spree,maybii/spree,jimblesm/spree,CiscoCloud/spree,yushine/spree,FadliKun/spree,vinayvinsol/spree,yushine/spree,progsri/spree,jeffboulet/spree,jimblesm/spree,azranel/spree,berkes/spree,alejandromangione/spree,cutefrank/spree,Lostmyname/spree,robodisco/spree,welitonfreitas/spree,volpejoaquin/spree,useiichi/spree,ayb/spree,yiqing95/spree,KMikhaylovCTG/spree,yushine/spree,kewaunited/spree,robodisco/spree,useiichi/spree,azranel/spree,NerdsvilleCEO/spree,jaspreet21anand/spree,volpejoaquin/spree,tomash/spree,TimurTarasenko/spree,firman/spree,DarkoP/spree,yiqing95/spree,CJMrozek/spree,zamiang/spree,sfcgeorge/spree,gregoryrikson/spree-sample,firman/spree,nooysters/spree,CiscoCloud/spree,jeffboulet/spree,softr8/spree,TrialGuides/spree,siddharth28/spree,jasonfb/spree,rakibulislam/spree,nooysters/spree,APohio/spree,tancnle/spree,rakibulislam/spree,vinsol/spree,ahmetabdi/spree,pervino/spree,groundctrl/spree,AgilTec/spree,piousbox/spree,jaspreet21anand/spree,Lostmyname/spree,maybii/spree,grzlus/spree,raow/spree,odk211/spree,wolfieorama/spree,jparr/spree,JuandGirald/spree,fahidnasir/spree,lsirivong/spree,wolfieorama/spree,alvinjean/spree,locomotivapro/spree,joanblake/spree,alvinjean/spree,ramkumar-kr/spree,mleglise/spree,Hawaiideveloper/shoppingcart,odk211/spree,ahmetabdi/spree,firman/spree,gregoryrikson/spree-sample,omarsar/spree,njerrywerry/spree,odk211/spree,AgilTec/spree,vmatekole/spree,jasonfb/spree,APohio/spree,vinayvinsol/spree,abhishekjain16/spree,quentinuys/spree,berkes/spree,sfcgeorge/spree,Kagetsuki/spree,calvinl/spree,vinsol/spree,gregoryrikson/spree-sample,rajeevriitm/spree,pulkit21/spree,welitonfreitas/spree,lyzxsc/spree,zaeznet/spree,NerdsvilleCEO/spree,edgward/spree,CiscoCloud/spree,priyank-gupta/spree,dafontaine/spree,hoanghiep90/spree,calvinl/spree,calvinl/spree,nooysters/spree,fahidnasir/spree,JDutil/spree,edgward/spree,fahidnasir/spree,reidblomquist/spree,Hawaiideveloper/shoppingcart,hoanghiep90/spree,trigrass2/spree,raow/spree,joanblake/spree,cutefrank/spree,nooysters/spree,vinsol/spree,vmatekole/spree,jparr/spree,sfcgeorge/spree