Change LAYOUT_SELECTION_CRITERIA IntDef

Added an LAYOUT_SELECTION_CRITERIA_UNSPECIFIED to the
LayoutSelectionCriteria interfacen a changed the other values as well.
ULocale can return "und" for undefined language tags,
so we convert those language tags to null, since we want to log them as "None" in
the KeyboardConfigured atom.

Bug: 280603577
Test: atest FrameworksServicesTests:KeyboardMetricsCollectorTests
Change-Id: I3d69cb924f661245502cf2bdecd9900988f4d890