NestedFolderPicker: Migrate to app platform API (#106926)

* Add /children endpoint

* Update folder client

* Add comment

* Add feature toggle

* Add new version of useFoldersQuery

* Error handling

* Format

* Rename feature toggle

* Remove options and move root folder constant

* Fix feature toggle merge

* Add feature toggle again

* Rename useFoldersQuery files

* Update API spec

* Fix test

* Add test

* Better typings

---------

Co-authored-by: Clarity-89 <homes89@ukr.net>

scripts/generate-rtk-apis.ts

@@ -57,7 +57,6 @@ const config: ConfigFile = {
     '../public/app/api/clients/folder/v1beta1/endpoints.gen.ts': {
       apiFile: '../public/app/api/clients/folder/v1beta1/baseAPI.ts',
       schemaFile: '../data/openapi/folder.grafana.app-v1beta1.json',
-      filterEndpoints: ['getFolder'],
       tag: true,
     },
     '../public/app/api/clients/advisor/v0alpha1/endpoints.gen.ts': {