[DocsUI M3] Uplift File list loading spinner

* update colors for the progress bar
* update colors for the pull-down-to-refresh spinner

Check the attached bug for demo video.

Bug: 377771889
Test: m DocumentsUIGoogle && manual inspection
Flag: com.android.documentsui.flags.use_material3
Change-Id: Ic36f563a1165a1ca9451b227fa2b373a2ceef0ca