Don't require post-execution state for onActivityResult

According to the documentation, onActivityResult() should be called
immediately before onResume(). This, however, was not always the case
in previous releases and fixing this caused some app compatibility
issues.
This CL removes required post execution state for ActivityResultItem.

Bug: 77695691
Test: ActivityLifecycleTests
Change-Id: Id8c02e9b49f9758aac616e37948570722d802de8