[REF] point_of_sale: update to the new module system

addons/point_of_sale/static/src/js/chrome.js

addons/point_of_sale/static/src/js/db.js

addons/point_of_sale/static/src/js/devices.js

addons/point_of_sale/static/src/js/gui.js

addons/point_of_sale/static/src/js/keyboard.js

addons/point_of_sale/static/src/js/main.js

addons/point_of_sale/static/src/js/models.js

addons/point_of_sale/static/src/js/popups.js

addons/point_of_sale/static/src/js/screens.js

addons/point_of_sale/static/src/js/tests.js

addons/point_of_sale/static/src/js/widget_base.js

addons/point_of_sale/views/templates.xml