[Code Improvement] Helper class for updating cart block

Problem/Motivation

As per #2920694-4: [Code Improvement] Unhardcode status message block id inside RefreshPageElementsHelper:

Considering that the approach for refreshing cart content will not be changed, so, in future I will have to split RefreshPageElementsHelper class into two. One will refresh the status message, and the other will refresh the cart.

There should be a helper class that would be responsible only for updating cart block.

More information: #2922378: [Code Improvement] Separate helper classes for updating cart block and status messages

Proposed resolution

Write the helper class.

Remaining tasks

Update kernel tests if necessary.

User interface changes

N/A

API changes

AjaxAddToCartForm::refreshAddToCartForm() may affect due to this change.

Data model changes

N/A