Clean up admin database page sidebar (#27364)

* Clean up tests

* Port `DatabaseFeature` type to `metabase-types/api`

* Add more tests

* Extract styled components

* Remove redundant class names

* Remove `"Actions"` CSS class

* Convert `Sidebar` to TypeScript

* Extract callbacks

* Remove redundant CSS classes

* Sort imports

* Extract more styled components

* That wasn't supposed to be here