DashboardScene: Support dashboard links (#77855)

* MenuItem: Allow react node as label

* LinkButton: Expose ButtonLinkProps

* Typecheck fix

* DashboardLinks: Refactor and use LinkButton and menu

* DashbaordLinks scene object

* Use flex layout for dashboard controls

* Update public/app/features/dashboard/components/SubMenu/DashboardLinksDashboard.tsx

Co-authored-by: Alex Khomenko <Clarity-89@users.noreply.github.com>

* fix keepTime and includeVars

* Add ellipsis to menu item label and description

* Use DashboardLink type from grafana/schema

* Update dashboard scene controls layout

* Fix e2e

* Test fix

* Bring back keyboard navigation

* Remove unused code

* One more fix

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Co-authored-by: Alex Khomenko <Clarity-89@users.noreply.github.com>
Co-authored-by: Torkel Ödegaard <torkel@grafana.com>

pkg/kinds/dashboard/dashboard_spec_gen.go

@@ -270,7 +270,7 @@ type Link struct {
 	Type LinkType `json:"type"`
 
 	// Link URL. Only required/valid if the type is link
-	Url string `json:"url"`
+	Url *string `json:"url,omitempty"`
 }
 
 // Dashboard Link type. Accepted values are dashboards (to refer to another dashboard) and link (to refer to an external resource)