Move the metric unit together with the label (in expanded view)

E.g. "Speed (km/h) / 100" instead of "Speed / 100 km/h"

Guarded by a temporary flag, so that we can experiment with both behaviors; the chosen one will be then merged with the main flag.

Bug: 434910979
Test: atest NotificationMetricStyleTest
Flag: android.app.api_metric_style
Flag: android.app.metric_style_unit_in_label
Change-Id: Ibac5fef55cc883272e7b22e4085592e3a34bcfcc