Implement nested collection item picker, use across app

frontend/src/metabase-lib/lib/Question.js

.../src/metabase/collections/containers/CollectionCreate.jsx

frontend/src/metabase/components/CreateDashboardModal.jsx

frontend/src/metabase/components/Select.jsx

frontend/src/metabase/components/SelectButton.jsx

frontend/src/metabase/components/form/FormField.jsx

frontend/src/metabase/components/form/FormWidget.jsx

frontend/src/metabase/components/form/StandardForm.jsx

...metabase/components/form/widgets/FormCollectionWidget.jsx

...tend/src/metabase/containers/AddToDashSelectDashModal.jsx

frontend/src/metabase/containers/CollectionMoveModal.jsx

frontend/src/metabase/containers/CollectionName.jsx

frontend/src/metabase/containers/CollectionPicker.jsx

frontend/src/metabase/containers/CollectionSelect.jsx

frontend/src/metabase/containers/DashboardForm.jsx

frontend/src/metabase/containers/DashboardPicker.jsx

frontend/src/metabase/containers/Form.jsx

frontend/src/metabase/containers/ItemName.jsx

frontend/src/metabase/containers/ItemPicker.jsx

frontend/src/metabase/containers/ItemSelect.jsx