DocsUI M3: Wrap calls to resources with helper

This is a preparation to be able to switch between material3
enabled/disabled within the same APK build.

Bug: 403375773
Test: m DocumentsUIGoogle && manual inspection
Flag: com.android.documentsui.flags.use_material3
BYPASS_LARGE_CHANGE_WARNING: Automated change

Change-Id: Ie0937149d9ca9bc141a4559c03c62f480b9a21b0