Remove the ssrRef from provider store

[obulat]

Problem

ssrRef from @nuxtjs/composition-api does not have a very good analog in Nuxt 3. In fact, it's not really needed in the store.

Description

The store state should be initiated once per user request in a plugin instead of the middleware that runs on every navigation.
An init-stores plugin can initialize the state of the provider store (fetching data from /stats endpoint), as well as setting the UI store state from cookies.

Alternatives

Additional context

Priority set to high because this is necessary for Nuxt 3 migration.