Don't report non-foldables as unfolded.

The FoldStateListener is reporting non-foldable phones as unfolded.
Previously, Falsing relied on this being null.

Inspect the foldability of a device directly and incorporate this into
the FalsingDataProvider.

Bug: 274914759
Test: manual && atest SystemUITests:com.android.systemui.classifier
Change-Id: Ibe768067d69464b14368ae0d67110453f9368c6a