RESTRICT AUTOMERGE Use consistent calling uid and package in navigateUpTo

Originally, if the caller of navigateUpTo is alive, even the calling
uid is set to the caller who launched the existing destination activity,
the uid from caller process has higher priority to replace the given
calling uid. So this change doesn't modify the existing behavior if
the caller process is valid. Besides, the case of delivering new intent
uses the source record as calling identity too, so the case of starting
new activity should be consistent.

Also forbid attaching null application thread to avoid unexpected state
in process record.

Bug: 144285917
Test: bit FrameworksServicesTests:com.android.server.am.ActivityStackTests
Change-Id: I60732f430256d37cb926d08d093581f051c4afed