With the initial layout of `provider/architecture`, after installing a
box with architecture support downgrading Vagrant would result in it
being unable to process the box collection. Swapping the layout to be
`architecture/provider` allows downgrades to still properly process the
box collection.
This commit attempts to uniquely identify the temporary files and
directories that are created during test runs. Where it was a quick
fix, this commit also removes the temporary files and directories.
There are still a ton of temporary files due to calls to
.isolated_environment in the tests without an easy API an easy way
to provide a closer to that function.
This involved defaulting all box searching at the moment to VirtualBox.
Additionally, box upgrading is not yet handled. This needs to be done at
some point.
The box collection can now find new-style boxes with providers and
return proper Box objects. In the future, we'll also have to implement
upgrading old style ones as well.
