testing: move arm system tests into their own folder

Prepare for expanding the arm system tests by cleaning up the test
directory.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20231120150833.2552739-11-alex.bennee@linaro.org>
3 files changed