health 2.0 vts: add battery current test.

Require the following on battery current:
- skip health info tests if current is 0 (indicates the value is unavailable)
- when charging, positive
- when discharging / not charging, negative
- when unknown, zero
- batteryCurrentAverage should be similar to batteryCurrentNow.

All new tests are executed over
a period of time to avoid effects of fluctuation in
battery current, and ensure battery status is initialized.

Requirements are enforced on devices launching with R
only.

Require the following on battery status:
- if not charging / full / charging, must be connected
- if discharging, must not be connected.

Test: run on coral, tests are skipped
Test: run on cuttlefish, test passes

Fixes: 136717180
Change-Id: Ic5a714b830ffeca1dcd000c6cad0fbfe8a8710ed
(cherry picked from commit 94841c9d)
Merged-In: Ic5a714b830ffeca1dcd000c6cad0fbfe8a8710ed