tests: add cpu tests to the new testing infrastructure

Change-Id: I42996ddc802ef279ab4970afc37cb0df25c04b08
Signed-off-by: Ayaz Akram <yazakram@ucdavis.edu>
Reviewed-on: https://gem5-review.googlesource.com/c/15857
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>