Switch LocalLog to using UTC / elapsed realtime

LocaleTracker can affect the devices time time zone. Using "local time"
for log timestamps for a component that can influence the device's time
zone makes interpreting logs harder. This change switches the
LocaleTracker's LocalLog over to using UTC and elapsed realtime for log
entry timestamps (as used in other components that affect time zone).

Bug: 227047106
Test: Build only
Change-Id: If83250e514fef84f46d1c85ecb956a7da7626f47