fix: removed possible memory leak in ssr

[ResuBaka]

Short Description and Why It's Useful

When current currentStoreView() is saved in an variable outside of the export it is not clean up automatically on the SSR side. To fix that I replaced all places that used the variable with the function call. Which fixes the problem.

The problem is currently not directly in the theme as in the default way the InstantCheckout.vue is not rendered on the SSR, but for every body that may change the theme and then renders the InstantCheckout.vue on SSR there it would lead to an memory leak so it should be fixed.

Which Environment This Relates To

Check your case. In case of any doubts please read about Release Cycle

• Test version (https://test.storefrontcloud.io) - this is a new feature or improvement for Vue Storefront. I've created branch from develop branch and want to merge it back to develop
• RC version (https://next.storefrontcloud.io) - this is a stabilisation fix for Release Candidate of Vue Storefront. I've created branch from release branch and want to merge it back to release
• Stable version (https://demo.storefrontcloud.io) - this is an important fix for current stable version. I've created branch from hotfix or master branch and want to merge it back to hotfix

Upgrade Notes and Changelog

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

IMPORTANT NOTICE - Remember to update CHANGELOG.md with description of your change

Contribution and Currently Important Rules Acceptance

• I read and followed contribution rules

[pkarw]

Thanks!