Use BatteryMeterDrawableBase as QS icon for Battery Saver

This ensures that QS, Settings, and Status bar all use the same drawable
base so they will always look the same. Battery saver is essentially a
full battery that always shows the power saver iconography.

Test: visual; runtest -x
frameworks/base/packages/SettingsLib/tests/integ/src/com/android/settingslib/graph/BatteryMeterDrawableBaseTest.java
Bug: 62668861
Change-Id: I8a9d5e59c9bb38c0ef794a0ed591195809521f70