Add start time to LmkKillOccurred

To accompany Piper cl/222070329 and https://googleplex-android-review.git.corp.google.com/c/platform/system/core/+/5578724

Bug: 119854389
Test: Manual
Change-Id: Ib2af1b66d4649279fdcb97e7cdf8cdb92e361765
Merged-In: Ib2af1b66d4649279fdcb97e7cdf8cdb92e361765
(cherry picked from Ib2af1b66d4649279fdcb97e7cdf8cdb92e361765)