* Drawer: add subtitle, expandable button and refactor style

* Drawer: update header style and z-index

* Drawer: refactor Drawer component and PanelInspector

* PanelInspector: add expandable

* Drawer: update stories with new props

* Inspector: rename InspectHeader -> InspectSubtitle

* Inspector: fix tabs spacing

* Drawer: remove z-index

* Update public/app/features/dashboard/components/Inspector/InspectSubtitle.tsx

Co-Authored-By: Dominik Prokop <dominik.prokop@grafana.com>

* Drawer: apply PR feedbacks

Co-authored-by: Dominik Prokop <dominik.prokop@grafana.com>