Indicate that a .xip was downloaded but hasn't been installed yet

[interstateone]

One of the more common failures I run in to is downloading the .xip and then not having enough space to unarchive it. Perhaps this could be indicated in the Xcode list UI somehow, so that it's clear that installing will continue from where it left off.

For example, we could use one of the shipping box symbols beside the Install button, with a .help(_:) modifier explaining what it indicates.

I'm not sure if users would want to abort installing the version they just previously intended to install, but allowing an option to delete the .xip without installing it may also be useful. If it's not clear where to put this option then don't let it block implementation of the first part.

[robmathers]

I'd second this for sure. Additionally it would be nice to have a way to reveal in Finder, so we can delete downloaded but not installed versions if we hit a disk space error.