arch, sim: Simplify the AuxVector type.

arch, sim: Simplify the AuxVector type.

The AuxVector type has a bunch of accessors which just give access to
the underlying variables through references. We might as well just make
those members accessible directly.

Also, the AuxVector doesn't need to handle endianness flips itself. We
can tell the byteswap mechanism how to flip an AuxVector, and let it
handle that for us.

This gets rid of the entire .cc file which was complicated by trying
to both hide the ISA specific endianness translations, and instantiate
templated functions in a .cc.

Change-Id: I433cd61e73e0b067b6d628fba31be4a4ec1c4cf0
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/18373
Maintainer: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>