Combine CpuTimePerUidFreq uids using base uids

http://ag/13181177 normalized uids to their base uids only for apps.
However, other processes (e.g. settings) run under multiple uids in some
cases too. So we need to normalize all uids.

Bug: 157535126
Test: cmd stats pull-source 10010
Change-Id: I427d84203ed97ab0b17890f06304cd4ff8a5c3b0