M3 migration follow-ups: VehicleOverlay accessibility + night theme dialog button style #1533
Description
Follow-up items from #1496 (M3 migration) to address in a fast-follow PR:
1. Accessibility regression: setOccupancyContentDescription dropped from VehicleOverlay
The refactored CustomInfoWindowAdapter in VehicleOverlay.java removed all three calls to UIUtils.setOccupancyContentDescription() while keeping the corresponding setOccupancyVisibilityAndColor() calls. This means the vehicle info window's occupancy indicator has no content description for screen readers.
Restore the three calls alongside each setOccupancyVisibilityAndColor() call with matching arguments.
2. Night theme customAlertDialogButton parent mismatch
values-night/themes.xml customAlertDialogButton inherits from Widget.MaterialComponents.Button.TextButton.Dialog, but values/themes.xml uses Widget.AppCompat.Button.ButtonBar.AlertDialog. This causes dialog buttons to render with different typography, padding, and corner radii between light and dark mode.
Fix: update the night theme to match the light theme's parent.