Dashboards: Add dashboard embed route (#69596)

* Dashboard embed: Set up route

* Dashboard embed: Cleanup

* Dashboard embed: Separate routes

* Dashboard embed: Render dashboard page

* Dashboard embed: Add toolbar

* Dashboard embed: Send JSON on save

* Dashboard embed: Add JSON param

* Dashboard embed: Make the dashboard editable

* Fix sending dashboard to remote server

* Add notifications

* Add "dashboardEmbed" feature toggle

* Use the toggle

* Update toggles

* Add toggle on backend

* Add get JSON endpoint

* Add drawer

* Close drawer on success

* Update toggles

* Cleanup

* Update toggle

* Allow embedding for the d-embed url

* Allow embedding via custom X-Allow-Embedding header

* Use callbackUrl

* Cleanup

* Update public/app/features/dashboard/containers/EmbeddedDashboardPage.tsx

Co-authored-by: kay delaney <45561153+kaydelaney@users.noreply.github.com>

* Use theme for spacing

* Update toggles

* Update public/app/features/dashboard/components/EmbeddedDashboard/SaveDashboardForm.tsx

Co-authored-by: Polina Boneva <13227501+polibb@users.noreply.github.com>

* Add select data source modal

---------

Co-authored-by: kay delaney <45561153+kaydelaney@users.noreply.github.com>
Co-authored-by: Polina Boneva <13227501+polibb@users.noreply.github.com>

docs/sources/setup-grafana/configure-grafana/feature-toggles/index.md

@@ -112,6 +112,7 @@ Experimental features might be changed or removed without prior notice.
 | `extraThemes`                               | Enables extra themes                                                                                         |
 | `lokiPredefinedOperations`                  | Adds predefined query operations to Loki query editor                                                        |
 | `pluginsFrontendSandbox`                    | Enables the plugins frontend sandbox                                                                         |
+| `dashboardEmbed`                            | Allow embedding dashboard for external use in Code editors                                                   |
 | `frontendSandboxMonitorOnly`                | Enables monitor only in the plugin frontend sandbox (if enabled)                                             |
 | `cloudWatchLogsMonacoEditor`                | Enables the Monaco editor for CloudWatch Logs queries                                                        |
 | `exploreScrollableLogsContainer`            | Improves the scrolling behavior of logs in Explore                                                           |