tests: Convert memtest to new framework

The original memtest is located at:
https://gem5.googlesource.com/public/gem5/+/master/tests/configs/memtest.py

Change-Id: I58be6fb1675f6502d6644d502915df80aa197a4a
Signed-off-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-on: https://gem5-review.googlesource.com/c/15836
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

tests: Convert tgen-simple-memory to new framework

The original test is located at:
https://gem5.googlesource.com/public/gem5/+/master/tests/configs/tgen-simple-mem.py

Change-Id: I13a58cfb3d01d08ef7c818fc00fb56ba126eb4b6
Signed-off-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-on: https://gem5-review.googlesource.com/c/15835
Reviewed-by: Rutuja Govind Oza <roza@ucdavis.edu>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>