[DocsUI M3] Move w700dp resources to w900dp

According to the new spec, 700dp is not a breakpoint any more,
moving all the resource files under 700dp to 900dp.

Bug: 380369329
Test: Manually inspect after deployment
Flag: com.android.documentsui.flags.use_material3
Change-Id: I17791d2acc68a37eecabdae98c603fcccb72444e