Improve X axis labels in battery chart (1)

Support showing labels under the trapezoids instead of between the
trapezoids. For daily chart, the labels are under the trapezoids, for
hourly chart, the labels are between the trapezoids.

Test: manual
Bug: 239491373
Bug: 236101166
Change-Id: I2efb5192d4baafc7745ce269224639511848293e