## Description

This PR adds one `ReorderableListView` example to demonstrate how `proxyDecorator` can be used to animate cards elevation.

https://user-images.githubusercontent.com/840911/236468570-d2b33ab3-6b6d-4f8d-90de-778dcf1ad8ce.mp4

For motivation, see https://github.com/flutter/flutter/issues/124729#issuecomment-1521524190.

## Related Issue

Fixes https://github.com/flutter/flutter/issues/124729

## Tests

Adds 1 tests.

This PR also moves some misplaced example tests from `examples/api/test/reorderable_list` to `examples/api/test/material/reorderable_list` (and replaces two existing ones).