[Discover] Create enhanced central state container

[kertal]

Summary

WIP to work on Discover's state management, it's scattered around the code base (saved search, appState, dataState via observables), cleaning, and centralizing stuff, not intended to be merged for now. This PR would be an intermediate step to clean up the current way centralized state is being handled. Its focus is to get a clearer structure, better separation from UI, removing of hook dependencies making it hard to debug the code. So refactoring without regressions, which makes it easier to further migrate to e.g. redux-toolkit

Parts of this PR

• Extending discover_state.ts, which was originally just used to access and sync appState with the URL. the new extended DiscoverStateContainer consists of 4 main parts (appState, savedSearch, dataState, internalState)
• Remove the useSavedSearch hook with it's endless hook dependencies
• Consolidation of the usage of searchSource and savedSearch. Despite searchSource being part of savedSearch, we were using those variables in parallel. Now savedSearch is part of DiscoverStateContainer, and this is used to get searchSource when needed
• Before this PR the state container was initialized twice, now there's just a single instance
• SearchSource is not used as intended. Now there's a parent searchSource, that's also persisted in the savedSearch saved object, and for fetching the document, histogram, the number of hits, volatile search sources children are created and additional parameters are applied.
• It adds a logger (addLog) function, that can be enabled using the browser's console, making it easier to debug state changes ... also for other use cases of course. By entering window?.ELASTIC_DISCOVER_LOGGER=true in the browser's console, logging messages are displayed in the console like this:
  This was very useful to debug, it was also helpful to add it in the root plugin of Discover for functional testing.
• There's now an "Unsaved changes" badge displayed, like in Dashboard when changes are applied to a new or persisted saved search.
  

DiscoverStateContainer

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
  /**
   * Internal state that's used at several places in the UI
   */
   internalState: InternalStateContainer;
...
some more stuff from the old container
...
 /**
  * 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;
  }
 /**
  * And even more functions
  **/
}

Checklist

• Unit or functional tests were updated or added to match the most common scenarios

For maintainers

• This was checked for breaking API changes and was labeled appropriately

[kibana-ci]

💚 Build Succeeded

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• Commit: 9d3ad3a
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Metrics [docs]

Module Count

Fewer modules leads to a faster build time

id	before	after	diff
discover	512	517	+5

Public APIs missing comments

Total count of every public API that lacks a comment. Target amount is 0. Run node scripts/build_api_docs --plugin [yourplugin] --stats comments for more detailed information.

id	before	after	diff
dataViewFieldEditor	30	32	+2
savedSearch	43	46	+3
total			+5

Async chunks

Total size of all lazy-loaded chunks that will be downloaded as the user navigates the app

id	before	after	diff
dataViewFieldEditor	154.4KB	154.4KB	-5.0B
discover	461.0KB	457.0KB	-4.0KB
total			-4.0KB

Page load bundle

Size of the bundles that are downloaded on every page load. Target size is below 100kb

id	before	after	diff
dataViewFieldEditor	22.8KB	22.8KB	+4.0B
discover	26.7KB	26.6KB	-70.0B
savedSearch	5.1KB	5.2KB	+54.0B
unifiedSearch	49.6KB	49.7KB	+30.0B
total			+18.0B

Unknown metric groups

API count

id	before	after	diff
dataViewFieldEditor	60	62	+2
savedSearch	43	46	+3
total			+5

async chunk count

id	before	after	diff
discover	10	11	+1

ESLint disabled line counts

id	before	after	diff
discover	35	37	+2

References to deprecated APIs

id	before	after	diff
discover	22	15	-7

Total ESLint disabled count

id	before	after	diff
discover	36	38	+2

History

• 💔 Build #83063 failed 8f265b3
• 💚 Build #82706 succeeded 3cda06f
• 💚 Build #82633 succeeded a082771
• 💔 Build #82570 failed e8558ab
• 💔 Build #82503 failed 567a752
• 💔 Build #82364 failed 9e4d706

To update your PR or re-run it, just comment with:
@elasticmachine merge upstream

cc @kertal

[kertal]

closing in favor of #153528

[kertal]

Closing since it's finished in #153528