[clang-tidy] bugprone-signal-handler improvements: display call chain

Display notes for a possible call chain if an unsafe function is found to be
called (maybe indirectly) from a signal handler.
The call chain displayed this way includes probably not the first calls of
the functions, but it is a valid possible (in non path-sensitive way) one.

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D118224