ApplicationExitInfo cleanup

This adds some missing IntDef values in the interface definition,
as well as in the toString implementation. Additionally adds missing
annotations for nullability and other IntDefs, and orders them according
to current code style.

Flag: EXEMPT cleanup
Bug: 281029564
Test: presubmit
Change-Id: Ia201c9d3fb2f8ae5ef82e122092089104b59089b