AppProfiler: don't hold lock for CPU times

AppProfiler doesn't need to lock when calling getCpuTimeForPid or
getCpuDelayTimeForPid.

Additionally, ProcessCpuTracker is locking just for the sake of
avoiding a long[4] allocation, which might have been necessary in 2009
for dalvik but isn't a concern now.

Test: presubmit
Bug: 270905745
Change-Id: I585b6113734850ef200fa3faccc1f6decab9389d