[Dashboard Navigation] Register alias with Visualizations plugin

[nickpeihl]

We should register the navigation embeddable alias with the Visualizations plugin so that saved objects can appear in the Visualize library.

We register the alias in the public/plugin.ts like this:

plugins.visualizations.registerAlias({
  aliasPath: '/',
  aliasApp: CONTENT_ID,
  name: CONTENT_ID,
  title: APP_NAME,
  icon: APP_ICON,
  description: '', // TODO
  stage: 'experimental' as VisualizationStage,
  appExtensions: {
    visualizations: {
      docTypes: [CONTENT_ID],
      searchFields: ['title^3'],
      toListItem(linkItem: NavigationEmbeddableCrudTypes['Item']) {
        const { id, type, updatedAt, attributes } = linkItem;
        const { title, description } = attributes;

        return {
          id,
          title,
          description,
          updatedAt,
          icon: APP_ICON,
          stage: 'experimental' as VisualizationStage,
          savedObjectType: type,
          typeTitle: APP_NAME,
          editUrl: '/',
        };
      },
    },
  },
});

However, the navigation embeddable does not have its own editor app. The aliasPath is required for applications to register with the visualizations alias registry. Since navigation embeddable does not have a separate editor application, we will need to change how we link to the flyout. We may create an ad-hoc editor application or change the VisTypeAliasRegistry definition to accept a function that opens an editor flyout.

Until we register the alias, the only way to delete Links panels that are saved to the library is via the Management - Saved Objects list view. Links panels saved to the Library can still be added to a Dashboard from the Add panel flyout.

[elasticmachine]

Pinging @elastic/kibana-presentation (Team:Presentation)