sim-se, tests: add a new sim-se test

This changeset adds a test to check the redirection features
added in faux-filesystem changeset. The test contains a
"chdir" system call to "/proc" which should be redirected to
"$(gem5-dir)/m5out/fs/proc" (as specified by the config files).

After "chdir", the test subsequently outputs the "/proc/cpuinfo"
file which should output a configuration of a fake cpu with
values set by a Python configuration file.

Note, the test will call "clone" once. To avoid a runtime error,
make sure that you run this test with "-n2" supplied to the
"config/example/se.py" script.

Change-Id: I505b046b7a4feddfa93a6ef0f0773ac43078cc94
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/17112
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>