shared/gpt: add entries for a bunch of architectures

shared/gpt: add entries for a bunch of architectures

I don't think we want people to send us pull requests over the next two years.
Let's just make something up ourselves, this is going to have at least as good
results, and will be much quicker.

Note that this only includes architectures for which there's some indication
that they are in active use. In architecture.h there are some more esoteric
ones like ARC_BE. We can add those if there's some actual user demand.

In particular, I included everything on the Debian "List of official ports" [1]
and a few other arches that we have received patches for in recent times.

[1] https://www.debian.org/ports/#portlist-released