Fix Process-Runtime field in crash dropbox headers

It was subtracting SystemClock.uptimeMillis() from a SystemClock.elapsedRealtime(), one of which includes time spent in deep sleep and one doesn't.

This changes the logic to use uptime for both, so the Process-Runtime will be the equal to the millis since boot not including time spent in deep sleep.

Fixes: 217357881
Test: atest FrameworksServicesTests:ActivityManagerTest
Change-Id: I3931a1df6f81992dea3c61cfb05094281cc3d605