feat(theme): add wishlist lazyload and totalItems shared field

[bartoszherba]

Description

Related Issue

Motivation and Context

Performance improvement

How Has This Been Tested?

• Check if the wishlist total count is loaded properly and displayed in the header when customers log in
• Check if wishlist is properly removed when customer log out
• Check if wishlist and its counter are properly updated when user add/remove item from wishlist

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.