Add TabletopModeController in WMShell

Populate the resource config that defines the horizontal fold and
together with the device posture to determine if the foldable device is
in tabletop mode or not.

Bug: 260871991
Test: atest WMShellUnitTests:TabletopModeControllerTest
Change-Id: I7878ec9ef95be39c2f1dc7ada7e7c871a018fa6e