[Discover] Migrate to react router

[kertal]

These are the 4 steps to get rid of angular router first routes in Discover need:

1. Migrate Context resolve part of the Angular route to be a hook of the main react component
   

   kibana/src/plugins/discover/public/application/angular/context.js

   Lines 35 to 40 in 0cfd04c

   	resolve: {
   	indexPattern: ($route, Promise) => {
   	const indexPattern = getServices().indexPatterns.get($route.current.params.indexPatternId);
   	return Promise.props({ ip: indexPattern });
   	},
   	},

2. Migrate Main resolve part of the Angular route to be a hook of the main react component
   

   kibana/src/plugins/discover/public/application/angular/discover.js

   Lines 61 to 75 in 6525105

   	resolve: {
   	savedObjects: function ($route, Promise) {
   	const history = getHistory();
   	const savedSearchId = $route.current.params.id;
   	return data.indexPatterns.ensureDefaultIndexPattern(history).then(() => {
   	const { appStateContainer } = getState({ history, uiSettings: config });
   	const { index } = appStateContainer.getState();
   	return Promise.props({
   	ip: loadIndexPattern(index, data.indexPatterns, config),
   	savedSearch: getServices()
   	.getSavedSearchById(savedSearchId)
   	.then((savedSearch) => {
   	if (savedSearchId) {
   	chrome.recentlyAccessed.add(
   	savedSearch.getFullPath(),

3. Apply the new folder structure (This ain't mandatory, but a nice to have) [Discover] Adapt new folder structure #101208
4. Migrate to react router e.g. like it's done in Visualize

   kibana/src/plugins/visualize/public/application/index.tsx

   Lines 30 to 40 in 4584a8b

   	const app = (
   	<Router history={services.history}>
   	<KibanaContextProvider services={services}>
   	<services.presentationUtil.ContextProvider>
   	<services.i18n.Context>
   	<VisualizeApp onAppLeave={onAppLeave} />
   	</services.i18n.Context>
   	</services.presentationUtil.ContextProvider>
   	</KibanaContextProvider>
   	</Router>
   	);

[elasticmachine]

Pinging @elastic/kibana-app (Team:KibanaApp)