Add a set of top insets when hiding status bar in 10:90 and 90:10

Adds back a "replacement" inset for the status bar when we hide it in 90:10 and 10:90. This ensures that app contents draw the same way in 70:30 and 90:10, even though we are hiding the status bar for 90:10.

Fixes: 434781199
Flag: com.android.wm.shell.enable_flexible_two_app_split
Test: Manual
Change-Id: I34603640277bca07cecd923be580c9527280924c