[SB][Chips] Add TimeSource in OngoingActivityChipModel.Active.Timer

We need to pass the time source in the view model to make it
easy to set a fake time in tests.

Bug: 372657935
Test: atest
SystemUIGoogleScreenshotTests:com.android.systemui.statusbar.chips.OngoingActivityChipsComposeScreenshotTest
Flag: com.android.systemui.status_bar_chips_modernization

Change-Id: I9277b504a1222f053250b14b38a2e885feb54dc0