ets: Increase data available in crash dumps and ets:info
erts: Add support for thread names
erts: Remove usage of QUANTIFY signal
erts: Introduce thread suspend functions

These functions allow any thread to suspend any other thread
immediately and then resume all threads. This is useful when
doing a crash dump in order to get a more accurate picture
of what state the system is in.
erts: Rename sys_sigset to sys_signal

Also removed old legacy fallback that is no longer used
erts: Improve crash dumps

This commit improves crash dumps in several ways:
  *  Suspends schedulers to get a current snapshot
  *  Dumps information about scheduler
  *  Dumps stack trace of current running process
     (including Garbing processes)