tests/acceptance: add reverse debugging test

tests/acceptance: add reverse debugging test

This is a test for GDB reverse debugging commands: reverse step and reverse continue.
Every test in this suite consists of two phases: record and replay.
Recording saves the execution of some instructions and makes an initial
VM snapshot to allow reverse execution.
Replay saves the order of the first instructions and then checks that they
are executed backwards in the correct order.
After that the execution is replayed to the end, and reverse continue
command is checked by setting several breakpoints, and asserting
that the execution is stopped at the last of them.

Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgalyuk@ispras.ru>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Willian Rampazzo <willianr@redhat.com>
--

v5:
 - disabled (as some other tests) when running on gitlab
   due to the unidentified timeout problem
Message-Id: <160174524678.12451.13258942849173670277.stgit@pasha-ThinkPad-X280>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>