healthd: Convert libhealthd_{draw,charger} to Soong.

Converting charger to Soong, one step at a time.

In the meantime, drop the use of BOARD_*/TARGET_* variables
in Android.mk because runtime sysprops will be used instead.
Libraries / binaries will always link to libminui / libpng /
libsuspend.

charger{.recovery,} can't be converted to Soong yet because
of the use of HAL_STATIC_LIBRARIES (Bug 127677771).

charger_test isn't converted because of the shared list
of CHARGER_{STATIC,SHARED}_LIBRARIES.

Bug: 124118169
Test: run charger on walleye

Change-Id: I355deda14e5b5c9938256ff0b778590ac0191095