* break out new and edit

* changed model to match new model in backend

* AlertingNG: API modifications (#30683)

* Fix API consistency

* Change eval alert definition to POST request

* Fix eval endpoint to accept custom now parameter

* Change JSON input property for create/update endpoints

* model adjustments

* set mixed datasource, fix put url

* update snapshots

* remove edit and add landing page

* remove snapshot tests ans snapshots

* wrap linkbutton in array

Co-authored-by: Sofia Papagiannaki <papagian@users.noreply.github.com>
Co-authored-by: Sofia Papagiannaki <sofia@grafana.com>