[SB][Battery] Protect against UnifiedBattery using too-big insets.

`inset` will inset the drawing space on both sides, which means that if
you inset by more than half of the available space, there's negative
room available and Compose will throw an exception.

Protect against that by never asking for an inset of more than half.

Bug: 400246091
Flag: com.android.settingslib.flags.new_status_bar_icons
Test: battery icon still renders correctly
Change-Id: Idcc41e19fe2268418c7f7bdc83acc2fe8aa71e04