tests: Add Jenkins presubmit and continuous test scripts

Note that continuous currently isn't used.

Change-Id: Ifcff88c8c4c75a9f630b97eaca22edd1681529c3
Signed-off-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/17456
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>