Cache monitored tag dump for watched clients when disconnected.

This CL updates the 'watch' command to allow monitoring specific
connected clients, and caches the latest monitored tags dump from
tracked clients when they disconnect.

This allows the 'watch' command to print tag information for short lived
camera sessions.

Specifically, this CL does the following:
- Adds fields to CameraService to track which clients should be watched
and cached
- Adds arguments to 'watch start' to allow passing tag list and client
list
- Renames 'watch live' to 'watch print' and prints cached dump for
disconnected watched clients.

Test: Manually tested
Bug: 199746421
Change-Id: I0931837fffcffc9005f57ad52d6f3cb390eba1d7