[DocsUI M3] Add wrapper for file row icons

* For thumbnail icons, show a border around it.
* For non-thumbnail icons or icons which fail to load thumbnail, show a
  white background wrapper.

Check the attached bug for demo video.

Bug: 389552458
Test: m DocumentsUIGoogle && manual inspection
Flag: com.android.documentsui.flags.use_material3
Change-Id: I40ab403fb3166be7376d0c3c3605f792151ce14d