Simplify export screen, unify with packaging

The export screen is/was such a monster. So many options, even more help text. Since people had issues with these options, I've decided to rework them in the import screen style. More verbose options, eliminating help text as much as possible. The packaging screen also had a project/release selection, which I've started to unify here. Added the same controls for project picking. For the release picking to be truly user friendly, it would be great to revive and make #219017: Selecting a project does not update release options work.

So before this patch:

After this patch: