Ref. #2262 Fix merging for category filter clear

[renatocason]

Related issues

#2262

Short description and why it's useful

Now on filter clear the GET has request={}, hence it loads the full catalog from Elasticsearch, not just the current category.

Upgrade Notes and Changelog

• No upgrade steps required (100% backward compatibility)
• I've updated the Upgrade notes and Changelog on how to port existing VS sites with this new feature

Contribution and currently important rules acceptance

• I read and followed contribution rules
• I read the TypeScript Action Plan and adjusted my PR according to it
• I read about Vue Storefront Modules and I am aware that every new feature should be a module

[patzick]

Thanks!:)