PowerMonitor trait objects can be used as a source of power supply data
and will be used by the goldfish battery. This CL includes a powerd backed
implementation of PowerMonitor available behind a feature flag which
receives updated data over D-Bus.
BUG=b:137890633
TEST=observe updated power data in ARCVM's /sys/class/power_supply at the end of this chain
Cq-Depend: chromium:2550102
Change-Id: Iacdc9bc7d11454d5b4f5d2639d19281174ad7e20
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2537349
Commit-Queue: Alex Lau <alexlau@chromium.org>
Tested-by: Alex Lau <alexlau@chromium.org>
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>