Don't reset the reported proc state while cleaning up the process

It'll be used to feed into the app kill stats.

Meanwhile, use the real process UID instead of the package UID for
indexing the app kill stats container internally, it'll be better
in terms of aligning with the caller UID in queries.

Bug: 194364213
Test: atest ApplicationExitInfoTest
Test: atest CtsAppExitTestCases:ActivityManagerAppExitInfoTest
Test: Manual - dumpsys activity exit-info
Change-Id: I5c966086bb90675294b5dfc1c5cdb0c163f05170