Ensure the reorder test runs on the foldable devices

It moves some classes form the Nexus package into the launcher package
so it can be used in both projects.

It also adds more test for foldables and test multiple
grids for each test.

Bug: 289584301
Fix: 291346193
Test: ReorderWidgets
Change-Id: I04db5f685d0344b8a3f3d42b429bbde061b3d8ea