healthd: charger loads resources from /product

Load resources from /product/etc/res/{values,images}/charger. If a
resource fails, falls back to /res/{values,images}/charger.

If the device has GSI flashed, resources may exist in both paths.
Resources in /product is used with a higher priority.

Test: turn off device, charge, observe animation
Bug: 119549685
Change-Id: I5a5143d132a0cc6ce9135469fb523feeeafd1b1b