[DocsUI M3] Restyle drag drop badge for M3

* When there are multiple dragging files:
  * add an additional drag layer
  * add a file counter
* Update drag show (radius/offset) to match the new M3 spec.
* drag shadow view is an isolated view without the theme
  context, so M3 color attributes like "?attr/colorXXX"
  can't be used directly, instead, system color tokens are
  being used in light/dark mode. Since system color tokens
  are only available in SDK 31, fallback static colors are
  being used in the original colors.xml.

Check the attached bug for demo.

Bug: 377771158
Test: m DocumentsUIGoogle && manual inspection
Flag: com.android.documentsui.flags.use_material3
Change-Id: Ia00bb0037a19813b4137d9d6cd7a42441b7f255e