[Discover] Refactor and simplify state container

[kertal]

Summary

Discover's state management is scattered around the code base (saved search, appState, dataState via observables, access and usage of search source, data view list state, ...). It should be cleaned up and centralized. Targets:

• A clearer structure
• Better separation from UI,
• Removing of hook dependencies making it hard to debug the code (recent implementations like ad-hoc data views and the Log explorer effort clearly showed it's pain points)
• Omit regressions
• Making it ready for next steps like migrating to redux-toolkit

There's already a state container in the code (discover_state.ts), which exports a function getState. it's primary usage is the providing appStateContainer, which is a redux like state container that's synced with the URL. This should be extended to be Discover's main state container by adding a "savedSearchContainer" and "dataStateContainer" and by providing functions to transform the state in the user interface. It could look like this:

export interface DiscoverStateContainer {
  /**
   * App state, the _a part of the URL - This is btw a redux like state
   */
  appStateContainer: ReduxLikeStateContainer<AppState>;
  /**
  * New, to access savedSearch related functionality (also for searchSource) 
  **/
  savedSearchContainer
 /**
 * New, data fetching related state migrated from `use_saved_search.ts`
 **/
  dataStateContainer
...
some more stuff from the old container, what's more we should have way to reload data views
...
 /**
functionality triggered from UI
**/
  actions: {
    resetSavedSearch: (id: string) => void;
    onOpenSavedSearch: (newSavedSearchId: string) => void;
    onUpdateQuery: (
      payload: { dateRange: TimeRange; query?: Query | AggregateQuery },
      isUpdate?: boolean
    ) => void;
    updateSavedQueryId: (newSavedQueryId: string | undefined) => void;
    /**
     * Pause the auto refresh interval without pushing an entry to history
     */
    pauseAutoRefreshInterval: () => Promise<void>;
    fetch: (reset?: boolean) => void;

  }
}

• POC: [Discover] Create enhanced central state container #140765
• Adding internal state container Issue: [Discover] Add internal state container #145074 PR: [Discover] Add container for internal state #144149
• Adding dataState container PR [Discover] Add container for data state (migrated from useSavedSearch hook) #148614
• Add saved search state
• Finish state container

[elasticmachine]

Pinging @elastic/kibana-data-discovery (Team:DataDiscovery)