Get rid of non-MobX methods from MobX stores

[brojd]

Currently in MobX stores we have methods that are none of the MobX entities (actions, computeds). Example:

getSearchResult(query = '') {
    if (!this.searchResult[query]) {
      return undefined;
    }
    return this.searchResult[query].map((msteamsChannelId: MSTeamsChannel['id']) => this.items[msteamsChannelId]);
  }

We should try to get rid of them so that in MobX stores we only have observables, computeds and actions. In the example above (and we have many such getSearchResult methods in different stores) we should check if this.searchResult is used anywhere else. If not, we should map it at the moment of saving in store instead of at the moment of retrieving from store. This way we will not need any mapping when getting search result and we will be able to consume observable directly from component