Looper: Add global and per process override for slow message threshold

Adds the log.looper.any.main.slow and log.looper.<PID>.any.slow
sysprops, which allows a global slow dispatch/delivery threshold to be
set for all running main loopers, as well as a threshold for all threads
within the process.

Having a single propery instead of needing to lookup uids for all apps
and then setting a threshold property for each thread makes manual
testing and debugging for slow looper messages easier.

Bug: 326356810
Test: manual - Setprop log.looper.slow.all_processes and observe log
Change-Id: I6fdb8b1ef51eedb6160963bef0e4b17eb2ea5494