[DocsUI M3] Uplift hover state in grid

Implement state_hovered="true" state for grid items. The following
combination states are implemented:
- hovered
- hovered+focused
- hovered+selected
- hovered+selected+focused

See bug for attached demo.

Bug: 401992851
Test: m DocumentsUIGoogle && manual inspection
Flag: com.android.documentsui.flags.use_material3
Change-Id: I25a3cbc760046016f03ae8fa2d3704ba024152f5