[SB][Chips] Add simple fade in / fade out animations to chips.

Only use the fade in & fade out if there's a single chip. If you have 2
chips then one chip disappears, the fade out looks not great.

Bug: 393581408
Bug: 364653005
Flag: com.android.systemui.status_bar_chips_modernization
Test: Trigger single notification chip, open & close app -> verify chip
fades out & in
Test: Trigger multiple notification chips, open & close each app ->
verify chips do no appearance or disappearance animation

Change-Id: Ib374e71da5cc3742a8c4108476209087d7e06d45