[DocsUI M3] Update empty state illustrations

* update empty state illustration (empty_m3.xml)
* update loading error illustration (hourglass.xml)
* add a search empty illustration (empty_search.xml), previously it
  points to empty.xml

Check the attached bug for screenshots.

Bug: 409697194
Test: m DocumentsUIGoogle && manual inspection
Flag: com.android.documentsui.flags.use_material3
Change-Id: Iba09fe4a0a4f74ff1493405afbd677dbe9b7b1e9