* Add XPath expressions
* Add "setCartQuantity" utility function
* Add "productIsInCart" utility function
* Add "update product qty" e2e test
* Clean up test file
* Fix test on headless mode
* Add Increase/Decrease qty test cases
* Decrease the query chain for better maintainability
* Rename expression functions/file for more clarity
* Resolve conflict with trunk
Co-authored-by: Saad Tarhi <saad.tarhi@automattic.com>