Fix WakelockTracer clock mis-match.

Both events and write should use elapsedRealtimeNanos (nanos since boot
including time suspended). To help with this, I've moved both into the
tracer class (it had been in Notifier to allow grabbing the time before
posting to the handler, but that's no longer the case).

Bug: 422797438
Test: atest PowerServiceTests
Flag: com.android.server.power.feature.flags.enable_app_wakelock_data_source
Change-Id: I611dfe304ce14ada4f1e77358829e3620c2d6ffa