Revert removal of Nav fallback auto embed (#59220)

*  Revert the changes that removed the feature

* Fix nits


Co-authored-by: Mamaduka <mamaduka@git.wordpress.org>
Co-authored-by: MaggieCabrera <onemaggie@git.wordpress.org>
Co-authored-by: kevin940726 <kevin940726@git.wordpress.org>

packages/core-data/src/resolvers.js

@@ -661,12 +661,42 @@ export const getUserPatternCategories =
 
 export const getNavigationFallbackId =
 	() =>
-	async ( { dispatch } ) => {
+	async ( { dispatch, select } ) => {
 		const fallback = await apiFetch( {
-			path: addQueryArgs( '/wp-block-editor/v1/navigation-fallback' ),
+			path: addQueryArgs( '/wp-block-editor/v1/navigation-fallback', {
+				_embed: true,
+			} ),
 		} );
 
+		const record = fallback?._embedded?.self;
+
 		dispatch.receiveNavigationFallbackId( fallback?.id );
+
+		if ( record ) {
+			// If the fallback is already in the store, don't invalidate navigation queries.
+			// Otherwise, invalidate the cache for the scenario where there were no Navigation
+			// posts in the state and the fallback created one.
+			const existingFallbackEntityRecord = select.getEntityRecord(
+				'postType',
+				'wp_navigation',
+				fallback.id
+			);
+			const invalidateNavigationQueries = ! existingFallbackEntityRecord;
+			dispatch.receiveEntityRecords(
+				'postType',
+				'wp_navigation',
+				record,
+				undefined,
+				invalidateNavigationQueries
+			);
+
+			// Resolve to avoid further network requests.
+			dispatch.finishResolution( 'getEntityRecord', [
+				'postType',
+				'wp_navigation',
+				fallback.id,
+			] );
+		}
 	};
 
 export const getDefaultTemplateId =