Percentage text now sits alongside the battery icon.

The old embedded percentage (introduced in change I6a3e7409) is hard
to read at status bar size, so we now draw it in a separate TextView to
the left (start) of the battery gauge. (The embedded code remains so
that it can be used by other places where the battery is drawn larger.)

The old system setting "status_bar_show_battery_percent" is still used
to control whether this percentage is shown, but note that it now
applies only to BatteryMeterView (i.e., the status bar) and not other
usages of BatteryMeterDrawable.

Bug: 32539932
Test: (manual) adb shell settings put system status_bar_show_battery_percent 1
Change-Id: Id298dba544f594b11269539284a2e8042fd4780b