[battery] add '?' state

This state represents the case when the battery is in an unknown state
which happens when `EXTRA_PRESENT` is `false` in the `BATTERY_CHANGED`
broadcast.

This is an existing feature of the old battery, so we should have it
here as well.

Test: adb shell am broadcast -a com.android.systemui.demo -e command battery -e present true
Test: BatteryInteractorTest
Test: BatteryViewModelBasedOnSettingTest
Fixes: 419820166
Flag: com.android.settingslib.flags.new_status_bar_icons
Flag: com.android.systemui.status_bar_root_modernization
Change-Id: Ia7b1ec01141c66b9cfe61c87db35534dfacb7a79