charger: Move built-in resources to /system

Convert rules to build charger resources to Soong
assuming BOARD_CHARGER_NO_UI is not set. As of now,
no devices in the source tree sets this variable. Also,
these images should be installed to the system image
regardless of this variable.

This change moves battery_fail and battery_scale to
/system/etc/res/images/charger.

Test: build and inspect system/etc/res/images/charger
Fixes: 143907179
Change-Id: Idccf5631371c7520cbfcfa6e92d1e88d0f3f95e7