NestedFolders: Nested folder picker (#70148)

* Initial layout

* Add some styles

* Add checkbox functionality

* Add feature flag

* Extract list component

* remove feature flag

* expand folders

* Don't show empty folder indicators in nested folder picker, prevent opening folder from selecting that folder

* remove legend and button

* selection stuff

* new feature flag just for nested folder picker

* fix lint

* cleanup

* fix movemodal not showing selected item

* refactor styles, make only label clickable

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Co-authored-by: Tobias Skarhed <tobias.skarhed@gmail.com>

packages/grafana-data/src/types/featureToggles.gen.ts

@@ -56,6 +56,7 @@ export interface FeatureToggles {
   mysqlAnsiQuotes?: boolean;
   accessControlOnCall?: boolean;
   nestedFolders?: boolean;
+  nestedFolderPicker?: boolean;
   accessTokenExpirationCheck?: boolean;
   showTraceId?: boolean;
   emptyDashboardPage?: boolean;