[SB][Chips] Allow up to 3 chips at the same time.

If the status_bar_chips_modernization flag is enabled, then the chips
Compose UI can very gracefully handle any number of chips. So, this CL
increases the max number of chips to 3 if that flag is on.

See demo video in bug.

Fixes: 392886257
Bug: 364653005
Flag: com.android.systemui.status_bar_chips_modernization
Flag: com.android.systemui.status_bar_notification_chips

Test: Trigger 3 chips, then fold & unfold -> verify you see 3 full-sized
chips in unfolded, 2 compact chips in folded
Test: Increase & decrease font size -> verify number of chips and chip
sizes respond appropriately
Test: atest OngoingActivityChipsWithNotifsViewModelTest

Change-Id: I3d8883ef1ed3b3458d71d3cd9511818d6b35c031