feat: add manjaro images

[boredland]

... and fix up some minor things I ran in along the way

[boredland]

@uraimo do you think I introduced the issue in the arch test or it it sth that is broken anyway?

[uraimo]

Hi, basically all the tests with archarm_latest are now failing on this branch and cancelling the jobs that come after them.
Something changed there, I've deleted the old images and trying to rebuild them from scratch.

[uraimo]

Failed again, let's try to temporarily remove archarm to see if the rest still works, it seems that this images is not like the others.

[boredland]

@uraimo sorry missed your PR, merged your change and lets see..

[boredland]

I think everything works, but fedora seems to have a new release so this is taking an absurd amount of time.

[boredland]

readded the --credential yes to qemu and a reference as to why.

[uraimo]

The problem with arch was related to the image from agners reporting linux/amd64 instead of a proper platform, the images should have been annotated as shown here.