Log timings for shutdown stages

Renamed BootTimingsTraceLog to TimingsTraceLog. It is now used for
 boot and shutdown logging.

Added measurements for main stages of shutdown in the system server:
ShutdownTiming: SendShutdownBroadcast took to complete: 734ms
ShutdownTiming: ShutdownActivityManager took to complete: 203ms
ShutdownTiming: ShutdownPackageManager took to complete: 17ms
ShutdownTiming: ShutdownBt took to complete: 533ms
ShutdownTiming: ShutdownRadio took to complete: 534ms
ShutdownTiming: ShutdownNfc took to complete: 1536ms
ShutdownTiming: ShutdownRadios took to complete: 1538ms
ShutdownTiming: ShutdownStorageManager took to complete: 906ms
ShutdownTiming: SystemServerShutdown took to complete: 3918ms

Bug: 64569080
Test: shutdown/reboot and check logs
Change-Id: I636c045852cd1ed6be1c58af6608f70e95756389