DO NOT MERGE Revert "Show dialog if top app is killed by lmk"

This reverts commit 84a2e2a0.

Comments in ag/3029299 for more details. This revert is dependent on another revert ag/3074066, which has been merged.

Reason for revert: No mechanism to check if an app is killed because of low memory killer

Bug:65488249
Test: manual
Change-Id: I2940a5b9f22f3428432537acbf64a10f81b0b9d0