Store SDK sandbox exit reasons under real UID and package UID

SDK sandbox processes have the same package UID, but have real UIDs
corresponding to the client app which started the sandbox. To allow SDKs
to view their own exit reasons, we need to store SDK sandbox exit
reasons under their real UID. To allow apps with the DUMP permission to
see exit reasons for all SDK sandboxes, we also store the same objects
under the package UID.

This requires additional logic to ensure the trace input is not reset if
already set.

Fixes: 241524222
Test: manual (kill sandbox process and call
getHistoricalProcessExitReasons from app w/ DUMP permission)
Test: manual (kill sandbox process and call
getHistoricalProcessExitReasons from SDK sandbox)
Test: atest SdkSandboxMetricsHostTest

Change-Id: I4279c22cbcb033b43013988c51fc441e4d2a66b7