Unblock device state callback in Window Extension.

Update DeviceStateManagerFoldingFeatureProducer to allow device state
callback off the main thread. Implement a lock to synchronize access to
the device state, ensuring thread-safety and immediate visibility of
updates from the binder thread to other threads. This allows device
state manager initialization within Activity#onCreate(), removing the
requirement to initialize WindowInfoTracker in an app initializer or
Application#onCreate().

Additional changes improve readability and add unit tests to verify the
new behavior. Notably, a new DeviceStateMapper class is introduced to
encapsulate the device state to posture mapping logic, limiting access
and ensuring immutability after initialization for thread safety.

Bug: 337820752
Test: atest WMJetpackUnitTests:DeviceStateManagerFoldingFeatureProducerTest
Flag: com.android.window.flags.wlinfo_oncreate
Change-Id: I8a4af1c5ac98f5653e4293a049291ba5ff7cd464