python: Fix weird memory issue in wrapped AddrRange vectors

There is a weird issue with the PyBind wrapper of
vector<AddrRange>. Assigning new values to a param that is a vector of
AddrRange sometimes results in an out-of-bounds memory access.

We work around this issue by treating AddrRange vectors as opaque
types. This slightly changes the semantics of the wrapper since Python
now manipulates the real object rather than a copy that has been
converted to a list.

Change-Id: Ie027c06e7a7262214b43b19a76b24fe4b20426c5
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Sascha Bischoff <sascha.bischoff@arm.com>
Reviewed-by: Curtis Dunham <curtis.dunham@arm.com>
Reviewed-by: Timothy Hayes <timothy.hayes@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/3223
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>