[flexiglass] Use the new compose battery icon in the shade header.

This is a re-implementation of ag/32105358.

Fix: 414597673
Fix: 413766503
Test: atest ShadeHeaderViewModelTest
Test: Manually tested by opening the shade with the old and new
 icon enabled, and observing it is rendered correctly in both cases.
Flag: com.android.systemui.scene_container
Flag: com.android.settingslib.flags.new_status_bar_icons
Change-Id: Iba184e50c0f6cedfdfe2ffce98a70e6d3860d99e