[DocsUI M3] update color for unit bar

* Update background color for the unit bar sort icon.
* Add ripple effect for the sort icon.
* Remove focus+hover state as per spec.

Check the attached bug for the demo.

Bug: 409697194
Test: m DocumentsUIGoogle && manual inspection
Flag: com.android.documentsui.flags.use_material3
Change-Id: I6d38e6660f35977693ae12b8af3d297d6e3060fd