feat(samples): UI clean-up, remove old assets

Summary:
Some of the UI buttons needed clean-up, mostly:

1. Making the sure material color matched the default button color.
2. Making hitboxes match the button sizes. The scene select buttons had bad hitboxes.
3. Updated the toggles menus to use our buttons in case people want them.
{F789136613}
4. Remove old `upperbody.png` file because we are not using them.
5. Enabled trilinear for the chair textures:
{F789137326}
6. Remove Inigo's assets because they were used by the stencil mirror, which no longer exists.

Reviewed By: andkim-meta

Differential Revision: D40954278

fbshipit-source-id: 960cb56e0d41399a22ebf713f2e0e7dbd3e23f98