PR11151: Recover stap_uprobes slots on process exit

PR11151: Recover stap_uprobes slots on process exit

When a process exits, it won't necessarily bother to munmap all of its
shared libraries.  This patch makes sure that with uprobes in libraries,
we still grab an exit notification and clear everything out.

* runtime/uprobes-common.c (stap_uprobe_process_munmap): New.
* tapsets.cxx (uprobe_derived_probe_group::emit_module_decls): Use above
  callback so that we can recover our resources on process exit.