Update the file list sort icon

This updates the sort icon that appears in the file list unit bar.
Currently it appears as a single arrow, this adds a background that is
properly styled along with keyboard interaction support.

Bug: 377771803
Test: atest SortDocumentUiTest#testSortByArrowIcon
Flag: com.android.documentsui.flags.use_material3

Change-Id: I46779db9ce7dc7c3caf3a4565be3ab9552dee1bf