sim-se: Switch to new MemState API

sim-se: Switch to new MemState API

Switch over to the new MemState API by specifying memory regions for
stack in each ISA, changing brkFunc to use MemState for heap memory,
and calling the MemState fixup in fixupStackFault (renamed to just
fixupFault).

Change-Id: Ie3559a68ce476daedf1a3f28b168a8fbc7face5e
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/25366
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>