Fix padding/styles used in Theme.DeviceDefault.AlertDialog.SettingsLib.Expressive

The total top gap should be 32px with the dialog content/description.
The bottom padding should be 24px. Also added colorAccent to ensure that
they are the same as the expressive design mock. Also added android: to
the attribute dialogPreferredPadding used

Test: manual and build
Fixes: 416089006
Flag: EXEMPT bugfix
Change-Id: Id8509e50e3c32fb0213ba4157a163c7da5437978