[DocsUI M3] Add height qualifier for medium/expanded layouts

Previously we were using medium layout (navigation rail) for devices
whose screen size is larger than 600dp, and using expanded layout
(permanent drawer) for devices whose screen size is larger than
900dp. Since these 2 layouts don't support collapsing app bar for
now, it causes issues when the device height is too small,
e.g. the file list/grid area is too small to view.

This CL adds a 600dp height qualifier for these 2 layouts,
essentially it renames the folders:
* xxx-w600dp -> xxx-w600dp-h600dp
* xxx-w900dp -> xxx-w900dp-h600dp
In a result, these 2 layouts will only take effects when both the
width and the height meet the requirements, i.e. if the device
height is smaller than 600dp, drawer_layout (which supports
collapsing app bar) will be used.

Check the attached bug for before/after comparison.

Bug: 402626151
Test: m DocumentsUIGoogle && manual inspection
Flag: com.android.documentsui.flags.use_material3
Change-Id: I491f8bb3b6fbb521bbd6a6be305ccd9f34f3e8a2