Ajaxify the update of cart block

• Issue [#2925451] by subhojit777: Update the module as per latest the Drupal Commerce
• Issue [#2923410] by subhojit777: [Code Improvement] dc_ajax_add_cart.refresh_page_elements_helper should be responsible for updating add to cart form
• Issue [#2919633] by subhojit777: [Code Improvement] Use container for loading services in RefreshPageElementsHelper
• Fixed a problem with Symfony ContainerInterface.
• Made `refreshAddToCartForm()` non-static so that it has access to the current form object. Thanks to https://api.drupal.org/comment/62339#comment-62339.
• Using `dc_ajax_add_cart.refresh_page_elements_helper` inside AjaxAddToCartForm.
• Updated tests.
• Issue [#2915360] by subhojit777: Review the approach of showing confirmation messages
• Issue [#2920694] by subhojit777: [Code Improvement] Unhardcode status message block id inside RefreshPageElementsHelper
• Issue [#2921187]: [Test Improvement] Check return type of RefreshPageElementsHelper update methods
• Issue #2910746 by subhojit777: Ajaxify the update of cart block
• Kernel tests for `getCartBlock()`, `updateCart()`, `updatePageElements()`.
• Update of cart block implemented.
• Tests updated.
• Issue [#2919191] by subhojit777: [Code Improvement] Remove the static usages of methods in RefreshPageElementsHelper
• Issue [#2917569] by subhojit777: [Code Improvement] Move methods for refreshing page elements into a helper class
• Negative tests added.
• Code updated as per the definition of `updateStatusMessages()`.
• Since `updateStatusMessages()` returns an object, `refreshAddToCartForm()` is updated so that it returns the output from `updateStatusMessages()`, rather than returning the updated response.
• Issue [#2910738] by subhojit777: Code improvements
• Added test message.
• Added notes for further improvements.