Add DEVICE_STATE_REAR_DISPLAY_OUTER_DEFAULT

Adds this new state which is the same as DEVICE_STATE_REAR_DISPLAY,
except with the additional property
PROPERTY_FEATURE_REAR_DISPLAY_OUTER_DEFAULT.

Note that this change/topic can be enabled even without the
System-UI-side change that actually displays a new dialog on the
inner display while in this mode. To the user, it will still be
exactly like the existing Rear Display Mode.

For the changes in this CL to take effect (regardless of the
SystemUI side), the corresponding changes must be done in the
device-specific overlays. Namely:

A) Add a new display layout that maps to the new device state (state 5)
   defined in BookStyleDeviceStatePolicy
B) Update the config_deviceStatesToReverseDefaultDisplayRotationAroundZAxis
   overlays to include state 5
C) Update the config_rearDisplayDeviceStates overlay to include state 5
D) Update the config_device_state_postures overlay to include state 5
E) Enable the flag

Bug: 371095273

Flag: android.hardware.devicestate.feature.flags.device_state_rdm_v2

Test: demo app
Test: atest WindowAreaComponentImplTests
Test: atest ExtensionRearDisplayTest

BYPASS_LARGE_CHANGE_WARNING

Change-Id: I4a4559649df6c37dc183514a38010dcab698b14d