[TP] Make all clocks a flow

1. From the clock registry we only have callbacks when clock list
   udpates. We need to have a flow instead of a one-off query which can
   possibly get list of only 1 clock because we query too early.
2. Decbounce the upstream signals to avoid multiple unnecessary updates
   of the carousel adapter

Test: tested that the clock carousel shows with all the clocks
Bug: 269656371
Change-Id: I63ef8ba62a32499f8213ef9d126e85fb211ce19e