feat: Renders Explore in SPA (#20572)

* feat: Renders Explore in SPA

* Adds permalink support

* Replaces navigation from Welcome page

* Fix initializing feature flags

* Remove redundant import

* Adds saveSlice workaround

* Fixes paths

* Fixes lint error

* Fixes tests

* Fix url to explore from Datasets view

* Fix explore page height

Co-authored-by: Kamil Gabryjelski <kamil.gabryjelski@gmail.com>

superset-frontend/src/explore/components/ExploreViewContainer/ExploreViewContainer.test.tsx

@@ -81,7 +81,7 @@ fetchMock.get('glob:*/api/v1/explore/form_data*', {});
 fetchMock.get('glob:*/favstar/slice*', { count: 0 });
 
 const renderWithRouter = (withKey?: boolean) => {
-  const path = '/superset/explore/';
+  const path = '/explore/';
   const search = withKey ? `?form_data_key=${key}&dataset_id=1` : '';
   return render(
     <MemoryRouter initialEntries={[`${path}${search}`]}>