[Ongoing call] Limit the chip background size to the status bar height.

Needed so that ag/23021476 doesn't cause the ongoing call chip
background to be cropped.

Bug: 272071029
Test: manual: use 200% font, trigger ongoing call chip -> verify
background isn't cut off
Test: manual: verify ongoing call chip background scales with different
sizes (see video attached to bug)
Test: manual: verify ongoing call chip in landscape still looks correct

Test: atest OngoingCallBackgroundContainerTest OngoingCallControllerTest

Change-Id: If0ceade1ef48845d39f76288bc91e3fe5f084534