[sanitizer] Move __sanitizer_set_death_callback to a more appropriate file

Summary:
`__sanitizer_set_death_callback` is a public interface function wrapping
`SetUserDieCallback`. Said function is defined in `sanitizer_termination.cc`,
which is not included in all the RT. Moving the interface function to that
file allows to not have a spurious public fuinction in RT that don't use it.

Reviewers: eugenis

Reviewed By: eugenis

Subscribers: kubamracek, delcypher, #sanitizers, llvm-commits

Differential Revision: https://reviews.llvm.org/D52363

llvm-svn: 342747